management information system controls and solves the business problems of an organization

8/4/2019 Management Information System Controls and Solves the Business Problems of an Organization

http://slidepdf.com/reader/full/management-information-system-controls-and-solves-the-business-problems-of 1/64

• Management information system controls and solves the business problems of an organization. These ana

other information systems by a group of methods that are humanly based or are supported by a dec

support system. MIS combines business with tech to help people in proving relevant information which

need to do their jobs faster and smarter.

I would like to list few important interview questions that are generally asked by an employer:

1. What duties does a manager of MIS perfo

The position of a manager of MIS is very responsible and challenging. He supervises the activities of MIS s

His main job is to identify the crucial business issues and yield workable solutions. These solutions may inc

activities like enhancing the existing applications and installing new software packages. He also prepares

manages the MIS capital budgets. Providing good and efficient training to the staff members is also unde

jurisdiction.

2. What qualifications do you have for this p

Tell about your qualifications. A bachelor’s degree in Business Administration or in Computer Science is the

requisite for this job. Tell about your working experience. You can also mention about your knowledg

system configuration, installation, administration and management. You should mention about your experi

in supporting financial and administrative systems.

3. What challenges do you see for the job you are apply

The question is very intelligent and same intelligence needs to be reciprocated here. Try to gain informa

about the organization through its website before hand. You can start your answer by saying that you h

always loved taking challenging positions and the one that is offered really suits your criteria. You can tell

good and efficient decision making skills are the most important factor required for this responsible posi

Also add that how your qualifications and experience qualify you for this

4. Did any time you had any problem implementing your own solut

Your previous experience is going to help you a lot while answering this question. You can tell about a m

problem that occurred at your previous work area and how did you solve it. What approach you took and

was the reason that made you do that. Be confident in yourself and genuine with your answer. You can also

about a common basic problem that generally occurs in this field and how you will approach to solve it.

These are some of the interview questions that are generally asked in an interview of a MIS manager. Al

best!

http://www.geekinterview.com/Interview-Questions/Oracle/Database-Administration

http://sql-plsql.blogspot.com/2009/04/sql-interview-questions.htmlonline interview

A computer programmer is a specialized person who designs, writes and tests the





computer programs. They are responsible for writing code that runs on client as well aserver side. He or she designs software programs through building logical work flowcharts, the functionality of which is translated into one of several computer languagescomputer programmer is also called a software developer, software engineer, computescientist, or software analyst.

In this article I would mainly provide you some interview questions that are frequentlyasked to the computer programmer. Let’s start with the first one.

1. What are linked list, binary tree, arrays, queues and strings?Well, it is one of the most frequently asked interview questions. The interviewer checkyour basic knowledge and understanding through this question. Linked list, binary treearrays, queues and strings are the elementary topics of programming. One should havgood command on the language on which he or she is working. Just prepare a short anwell organized answer to this question before appearing in front of the interviewer.

2. What is the difference between TCP and UDP? TCP stand for transmission control protocol and UDP stands for User datagramProtocol.TCP is a reliable and connection oriented protocol, if there has been any mistathen TCP resends the part that was corrupted whereas UDP is an unreliable andconnection-less protocol. A TCP protocol sends the data in a serial manner but a UDPprotocol does not sends the data in serial order.

3. What is the difference between calloc() and malloc() function?A calloc function allocates a block of memory for an array of elements of a certain sizewhereas a malloc function allocates bytes of memory and not blocks of memory likecalloc. A malloc function returns a void pointer to the allocated space or NULL if there

insufficient memory available whereas a calloc function allocates an array in memorywith elements initialized to 0 and returns a pointer to the allocated space.

4. State some sorting methods. There are various sorting techniques such as quick sort, merge sort, binary sort, radixsort etc. The quick sort algorithm works on divide and conquer rule. A merge sortalgorithm works by considering the data to be sorted as a sequence of already-sortedlists and radix sort technique takes a list of integers and puts each element on a smalllist, depending on the value of its least significant byte.

Well, these are some of the frequently asked interview questions. I am very sure my

article would surely help you to answer the questions with great confidence.

• Oracle developer is responsible for developing a database for the company. He is the main architect of the datab

management system of the organization. He modifies the project to suit the current needs. Hence a good knowle



of SQL, PL/SQL with proficiency in Oracle is a must for this field. Gaining a certificate from an organization will he

lot to excel in this field.

The career is promising and can earn you high rewards. Now I would like to list few important interview questions

are generally asked by an employer for an Interview of an Oracle Developer:

1. Tell us about your qualificati

The question is very important for you to tell about your capability for the job. If you are certified programmer th

will be easier for you. Give details about your qualifications. Mention your important projects. If you have achie

some applause for your work then do mention.

2. Give a relation between Database, Tablespace and Data

A database is divided logically to comprise one or more tablespaces. Each tablespace is consisted of one or more

files.

3. Give the components of physical database struc

Oracle Database physical structure comprise of:

1. 1. Data Files: These are .dbf file. These occupy fixed size on the hard disk. A data file contains a data b

ow id and Table clusters.

2. 2. Control Files: It contains configuration parameters. It is basically used to depict one slot per data file.

xtension for the file is .ctl.

3. 3. Online Redo Log Files: These files have an extension .rdo and .arc

4. 4. Trace Files: These are .trc files. These save traces of the user session.

5. 5. Password Files: These are the file used for security purpose.

6. 6. sidALTR files : These are the log critical files.

4. Give a command to find the time zone in which a database is operaThe command that can give result for this query is:

SELECT DBTIMEZONE FROM DUAL;

5. What are redo l

Redo logs are physical and logical structures that hold the alterations made in a database. Redo logs are usefu

times when recovery of database is done.

6. What do you mean by coalescing a tablespa

Coalescing is used to utilize defragment space and dictionary managed tablespace for combining neighboring ext

into a single extent.

These are the few important interview questions that are generally asked by an employer in an interview of an Or

Developer. All the Best!



Management Interview Questions

You can expect to see the following management interview questions on your next interview if you are interviewingpositions in management, project management, or even team leader positions.

. How would your co-workers describe you?Management Interview questions like this are generally asked to discover additional hidden qualities about yourselfhat you might not otherwise have mentioned.

My co-workers will tell you that I am a team player and a colleague they can count on to pull his weight whether itnormal day or we’re in a crunch.”

2. What is your viewpoint of management?

nterview questions for management like this are asked to find out what kind of leader you are. Should you ever getplaced in a management role, how will you delegate the workload or teach your co-workers.

I believe the main goal of any management position is to get things done by evenly distributing the workload to themost qualified members of the team. They also make sure that each member of the team has all the resources andraining that are necessary to complete the job. They are loyal and are always working in the best interest of theompany. Their job is tough; they must evaluate employee performance, empower members of the team and be abledentify those who are not pulling their own weight.”

3. What is your definition of success?

The interviewer is looking for work related examples of how you measure success and when know you have reacheaccomplishment. Use a work related example and keep your answer short and to the point.

In my opinion and as it relates to the workplace, success is a measurable variable. If you don’t measure your

accomplishments, success is lost. Success can be tied to everything you do each day. If I plan to accomplish 3 tasksbefore the end of the day and I do so, then I have been successful. Success simply means accomplishing what you sout to do within the parameters you specify, whether they be time, money or learning, etc.”

4. What is your definition of failure?

This question is really just the opposite of your definition of success. What does failure mean to you and how do yoknow you have failed within a given timeframe. Keep in mind that failure is just a perspective.



For starters, failure is an event and not a person and you only fail if you quit and I’m not a quitter. I may not compla project on time or miss an important deadline, but that does not qualify as having failed in my book. If I complete ask, but miss a deadline, I still consider it a success because I finished, but without the desired result.”

5. Do you know who our competitors are?

Do your homework and research the company and find out who are their competitors. Management interview questiike this will quickly reveal how well you conducted your research prior to the interview. If you did your homeworkhen you’re telling the interviewer that you are serious about this job and it’s that little extra effort that you show in nterview that will clearly separate you from your competition. Now, if you are interviewing at General Electric,

obviously they have thousands of competitors as they make thousands of products. So do your homework.

Yes, I work for one of them but I have always admired your company and have always wanted to work here.”

6. Do you feel that you are an organized person?

They are not asking if you keep a messy desk. Don’t reveal any organizational flaws you may have as that will be atrike against you and if you do have your act together, don’t come across as being a neatness freak either. Instead,

peak of your ability to manage time and workload.

Yes, I consider myself to be very well organized. Everyday when I arrive at work, I check my email and messagesThen I plan out exactly what I am going to do that day. Even if I already know that I am going to work on the Johnsproposal, I still review my current status and set my goals for the day. At the end of the day, I review my progress anplan for the following day.”

7. How do you manage your time?

Obviously, your answer should reflect that you are a self starter and never put things off. They want to hear that yougoals for your work and how you prioritize them.

I only have so many hours in the day to get my work done and I have found that if I don’t create daily, weekly, andmonthly goals, it seems like nothing ever gets done. I keep track of all my responsibilities and goals in spreadsheet aeview them daily. I mark down when I am first assigned a task, how long I think it will take, when it needs to beompleted and how much time I will need to spend on it each day to complete the job on time. This helps me in so

many ways, but mainly it keeps me on track with what is important. It also helps me from getting overbooked andpromising more than I can deliver. Now, I can always deliver what I promise and be on-time.”

8. We are a fast moving company and things are always changing, how do you think you will fit in with our ev

hanging and fast paced environment?

This question is best answered with an example from one of your past jobs that casts you in the spotlight showing andemonstrating your capabilities of handling change.

Our company has 20 field sales reps and they need to receive their email on the cell phone. This is something the Idepartment knows little about and has never supported mobile devices for a variety of reasons. The request came dofrom the president and we needed to make this happen immediately. I was out of my element on this one and knewittle about the subject, but I was assigned the entire task with a short deadline. So I researched the various technologhat would support our needs, tested several of them and after 3 weeks of hard work I presented my findings to the s

department and allowed them to make a decision on one of the three options. Once they accepted, I soon got to workand within two weeks every sales person could now retrieve their mail from their cell phone any where in the world



Oracle Database Administration (DBA) Interview

Questions (Technical)

Here are some of the Common InterviewQuestions for Oracle DatabaseAdministrator. As of now it contains 1Questions. These questions are commfor both Senior Oracle DBA or Junior DBA. I have divided the questions intcategories Technical InterviewQuestions, Unix Related questions asto an Oracle Database Administrator

(DBA) and Backup and RecoveryInterview Questions commonly askedOracle DBA interview

. What is an Oracle Instance?

2. What information is stored in Control File?

. When you start an Oracle DB which file is accessed first?

4. What is the Job of SMON, PMON processes?

. What is Instance Recovery?

6. What is written in Redo Log Files?

7. How do you control number of Datafiles one can have in an Oracle database?

8. How many Maximum Datafiles can there be in an Oracle Database?

9. What is a Tablespace?

0. What is the purpose of Redo Log files?

11. Which default Database roles are created when you create a Database?

2. What is a Checkpoint?

3. Which Process reads data from Datafiles?



4. Which Process writes data in Datafiles?

5. Can you make a Datafile auto extendible. If yes, how?

6. What is a Shared Pool?

7. What is kept in the Database Buffer Cache?

8. How many maximum Redo Logfiles one can have in a Database?

9. What is difference between PFile and SPFile?

20. What is PGA_AGGREGRATE_TARGET parameter?

1. Which types of backups you can take in Oracle?

2. A database is running in NOARCHIVELOG mode then which type of backups you can take?

2.3. Can you take partial backups if the Database is running in NOARCHIVELOG mode?

4. Can you take Online Backups if the the database is running in NOARCHIVELOG mode?

5. How do you bring the database in ARCHIVELOG mode from NOARCHIVELOG mode?

6. You cannot shutdown the database for even some minutes, then in which mode you should runthe database?

7. Where should you place Archive logfiles, in the same disk where DB is or another disk?

8. Can you take online backup of a Control file if yes, how?

9. What is a Logical Backup?

10. Should you take the backup of Logfiles if the database is running in ARCHIVELOG mode?

11. Why do you take tablespaces in Backup mode?



12. What is the advantage of RMAN utility?

13. How RMAN improves backup time?

14. Can you take Offline backups using RMAN?

15. How do you see information about backups in RMAN?

16. What is a Recovery Catalog?

17. Should you place Recovery Catalog in the Same DB?

18. Can you use RMAN without Recovery catalog?

19. Can you take Image Backups using RMAN?

20. Can you use Backupsets created by RMAN with any other utility?

Backup and Recovery Interview Questions for an

Oracle DBA Page 2

Some of the Common Backup and RecoveryInterview Questions for Oracle DatabaAdministrator. These questions arecommon for both Senior Oracle DBA oJunior DBA. I have compiled thesequestions based upon the feedback I from many candidates who haveattended interviews in various MNC's

21. Where RMAN keeps information of backups if you are using RMAN without Catalog?

22. You have taken a manual backup of a datafile using o/s. How RMAN will know about it?

23. You want to retain only last 3 backups of datafiles. How do you go for it in RMAN?

24. Which is more efficient Incremental Backups using RMAN or Incremental Export?



25. Can you start and shutdown DB using RMAN?

26. How do you recover from the loss of datafile if the DB is running in NOARCHIVELOG mode?

27. You loss one datafile and it does not contain important objects. The important objects are there in other datafileswhich are intact. How do you proceed in this situation?

28. You lost some datafiles and you don't have any full backup and the database was running in NOARCHIVELOGmode. What you can do now?

29. How do you recover from the loss of datafile if the DB is running in ARCHIVELOG mode?

0. You loss one datafile and DB is running in ARCHIVELOG mode. You have full database backup of 1 week oldand partial backup of this datafile which is just 1 day old. From which backup should you restore this file?

1. You loss controlfile how do you recover from this?

2. The current logfile gets damaged. What you can do now?

3. What is a Complete Recovery?

4. What is Cancel Based, Time based and Change Based Recovery?

5. Some user has accidentally dropped one table and you realize this after two days. Can you recover this table if thDB is running in ARCHIVELOG mode?

6. Do you have to restore Datafiles manually from backups if you are doing recovery using RMAN?

7. A database is running in ARCHIVELOG mode since last one month. A datafile is added to the database last weeMany objects are created in this datafile. After one week this datafile gets damaged before you can take any backupNow can you recover this datafile when you don't have any backups?

8. How do you recover from the loss of a controlfile if you have backup of controlfile?

9. Only some blocks are damaged in a datafile. Can you just recover these blocks if you are using RMAN?

40. Some datafiles were there on a secondary disk and that disk has become damaged and it will take some days to ga new disk. How will you recover from this situation?

41. Have you faced any emergency situation. Tell us how you resolved it?

42. At one time you lost parameter file accidentally and you don't have any backup. How you will recreate a newparameter file with the parameters set to previous values.



n response for a reader of this blog who asked me for some interview questions for a 3+Year experienced DBA, I hwritten this series of questions that you can use in your interviews. Either if you are the interviewer, or the interviewEnjoy!

. Basic (Every DBA should answer correctly ALL these questions. This knowledge is just basic for a 3+ year xperienced DBA).1 Q- Which are the default passwords of SYSTEM/SYS?

A- MANAGER / CHANGE_ON_INSTALL

.2 Q- How can you execute a script file in SQLPLUS?A- To execute a script file in SQLPlus, type @ and then the file name.

.3 Q- Where can you find official Oracle documentation?A- tahiti.oracle.com.4 Q- What is the address of the Official Oracle Support?

A- metalink.oracle.com or support.oracle.com.5 Q- What file will you use to establish Oracle connections from a remote client?

A- tnsnames.ora.6 Q- How can you check if the database is accepting connections?

A- lsnrctl status or lsnrctl services.7 Q- Which log would you check if a database has a problem?

A- Alert log.8 Q- Name three clients to connect with Oracle, for example, SQL Developer:A- SQL Developer, SQL-Plus, TOAD, dbvisualizer, PL/SQL Developer… There are several, but an experienced dbhould know at least three clients..9 Q- How can you check the structure of a table from sqlplus?

A- DESCRIBE or DESC.10 Q- What command will you start to run the installation of Oracle software on Linux?

A- runInstaller

2. Moderate (Standard knoledge for a daily-work of every DBA. He could fail one or two questions, but not more)2.1 Q- What should you do if you encounter an ORA-600?A- Contact Oracle Support2.2 Q- Explain the differences between PFILE and SPFILEA- A PFILE is a Static, text file that initialices the database parameter in the moment that it’s started. If you want tomodify parameters in PFILE, you have to restart the database.A PFILE is a dynamic, binary file that allows you to overwrite parameters while the database is already started (withome exceptions)

2.3 Q- In which Oracle version was Data Pump introduced?A- Oracle 10g



2.4 Q- Say two examples of DML, two of DCL and two of DDLA- DML: SELECT, INSERT, UPDATE, DELETE, MERGE, CALL, EXPLAIN PLAN, LOCK TABLEDDL: CREATE, ALTER, DROP, TRUNCATE, COMMENT, RENAMEDCL: GRANT, REVOKE2.5 Q- You want to save the output of an Oracle script from sqlplus. How would you do it?

A- spool script_name.txtelect * from your_oracle_operations;pool off;

2.6 Q- What is the most important requirement in order to use RMAN to make consistent hot backups?A- Your database has to be in ARCHIVELOG mode.2.7 Q- Can you connect to a local database without a listener?A- Yes, you can.2.8 Q- In which view can you find information about every view and table of oracle dictionary?A- DICT or DICTIONARY2.9 Q- How can you view all the users account in the database?A- SELECT USERNAME FROM DBA_USERS;

2.10 Q- In linux, how can we change which databases are started during a reboot?A- Edit /etc/oratab

. Advanced (A 3+ year experienced DBA should have enough knowledge to answer these questions. However,depending on the work he has done, he could still fail up to 4 questions).1 Q- When a user process fails, what Oracle background process will clean after it?

A- PMON.2 Q- How can you reduce the space of TEMP datafile?

A- Prior to Oracle 11g, you had to recreate the datafile. In Oracle 11g a new feature was introduced, and you can shhe TEMP tablespace..3 Q- How can you view all the current users connected in your database in this moment?

A- SELECT COUNT(*),USERNAME FROM V$SESSION GROUP BY USERNAME;.4 Q- Explain the differences between SHUTDOWN, SHUTDOWN NORMAL, SHUTDOWN IMMEDIATE ANSHUTDOWN ABORTA- SHUTOWN NORMAL = SHUTDOWN : It waits for all sessions to end, without allowing new connections.SHUTDOWN IMMEDIATE : Rollback current transactions and terminates every session.SHUTDOWN ABORT : Aborts all the sessions, leaving the database in an inconsistent state. It’s the fastest methodbut can lead to database corruption..5 Q- Is it possible to backup your database without the use of an RMAN database to store the catalog?

A- Yes, but the catalog would be stored in the controlfile..6 Q- Which are the main components of Oracle Grid Control?

A- OMR (Oracle Management Repository), OMS (Oracle Management Server) and OMA (Oracle ManagementAgent)..7 Q- What command will you use to navigate through ASM files?

A- asmcmd.8 Q- What is the difference between a view and a materialized view?

A- A view is a select that is executed each time an user accesses to it. A materialized view stores the result of this qun memory for faster access purposes..9 Q- Which one is faster: DELETE or TRUNCATE?

A- TRUNCATE



A- Trick question: you can’t do that, at least with any Oracle tool. A very experienced DBA should perfectly know .8 Q- SQL> SELECT * FROM MY_SCHEMA.MY_TABLE;

SP2-0678: Column or attribute type can not be displayed by SQL*PlusWhy I’m getting this error?A- The table has a BLOB column.

.9 Q- What parameter will you use to force the starting of your database with a corrupted resetlog?A- _ALLOW_RESETLOGS_CORRUPTION

.10 Q- Name the seven types of Oracle tablesA- Heap Organized Tables, Index Organized Tables, Index Clustered Tables, Hash Clustered Tables, Nested TablesGlobal Temporary Tables, Object Tables.



General Questions

Tell us about yourself/ your background.

What are the three major characteristics that you bring to the job market?

What motivates you to do a good job?

What two or three things are most important to you at work?

What qualities do you think are essential to be successful in this kind of work?

What courses did you attend? What job certifications do you hold? What subjects/courses did you excel in? Why?

What subjects/courses gave you trouble? Why?

How does your previous work experience prepare you for this position?

How do you define 'success'?

What has been your most significant accomplishment to date?

Describe a challenge you encountered and how you dealt with it.

Describe a failure and how you dealt with it.

Describe the 'ideal' job... the 'ideal' supervisor.

What leadership roles have you held?

What prejudices do you hold?

What do you like to do in your spare time?

What are your career goals (a) 3 years from now; (b) 10 years from now?

How does this position match your career goals?

What have you done in the past year to improve yourself?

In what areas do you feel you need further education and training to be successful?

What do you know about our company?

Why do you want to work for this company. Why should we hire you? Where do you see yourself fitting in to this organization ...initially? ...in 5 years?

Why are you looking for a new job?

How do you feel about re-locating?

Are you willing to travel?

What are your salary requirements?



Faster access to data blocks in a table.9. Give the two types of tables involved in producing a star schema and the type of datathey hold.

Fact tables and dimension tables. A fact table contains measurements while dimension

tables will contain data that will help describe the fact tables.10. What type of index should you use on a fact table?

A Bitmap index.11. Give some examples of the types of database contraints you may find in Oracle andindicate their purpose.

A Primary or Unique Key can be used to enforce uniqueness on one or more columns.

A Referential Integrity Contraint can be used to enforce a Foreign Key relationship

between two tables.

A Not Null constraint - to ensure a value is entered in a column

A Value Constraint - to check a column value against a specific set of values.12. A table is classified as a parent table and you want to drop and re-create it. How wouldyou do this without affecting the children tables?

Disable the foreign key constraint to the parent, drop the table, re-create the table, enable

the foreign key constraint.13. Explain the difference between ARCHIVELOG mode and NOARCHIVELOG mode andthe benefits and disadvantages to each.

ARCHIVELOG mode is a mode that you can put the database in for creating a backup of all

transactions that have occurred in the database so that you can recover to any ball in time.

NOARCHIVELOG mode is basically the absence of ARCHIVELOG mode and has the

disadvantage of not being able to recover to any ball in time. NOARCHIVELOG mode does

have the advantage of not having to write transactions to an archive log and thus increases

the performance of the database slightly.14. What command would you use to create a backup control file?

Alter database backup control file to trace.15. Give the stages of instance startup to a usable state where normal users may access it.

STARTUP NOMOUNT - Instance startup

STARTUP MOUNT - The database is mounted

STARTUP OPEN - The database is opened

16. What column differentiates the V$ views to the GV$ views and how?

The INST_ID column which indicates the instance in a RAC environment the information

came from.17. How would you go about generating an EXPLAIN plan?

Create a plan table with utlxplan.sql.

Use the explain plan set statement_id = 'tst1' into plan_table for a SQL statement

http://www.orafaq.com/wiki/Bitmap_index





Look at the explain plan with utlxplp.sql or utlxpls.sql18. How would you go about increasing the buffer cache hit ratio?

Use the buffer cache advisory over a given workload and then query the

v$db_cache_advice table. If a change was necessary then I would use the alter system set

db_cache_size command.19. Explain an ORA-01555.

You get this error when you get a snapshot too old within rollback. It can usually be solved

by increasing the undo retention or increasing the size of rollbacks. You should also look at

the logic involved in the application getting the error message.20. Explain the difference between $ORACLE_HOME and $ORACLE_BASE.

ORACLE_BASE is the root directory for oracle. ORACLE_HOME located beneath

ORACLE_BASE is where the oracle products reside.

[edit] Oracle Interview Questions1. How would you determine the time zone under which a database was operating?

using SELECT dbtimezone FROM DUAL;2. Explain the use of setting GLOBAL_NAMES equal to TRUE.

It ensure the use of consistent naming conventions for databases and links in a networked

environment.3. What command would you use to encrypt a PL/SQL application?4. Explain the difference between a FUNCTION, PROCEDURE and PACKAGE.5. Explain the use of table functions.6. Name three advisory statistics you can collect.7. Where in the Oracle directory tree structure are audit traces placed?8. Explain materialized views and how they are used.9. When a user process fails, what background process cleans up after it?

It is PMON.

10. What background process refreshes materialized views?11. How would you determine what sessions are connected and what resources they arewaiting for?12. Describe what redo logs are.13. How would you force a log switch?

alter system switch logfile;

14. Give two methods you could use to determine what DDL changes have been made.15. What does coalescing a tablespace do?16. What is the difference between a TEMPORARY tablespace and a PERMANENTtablespace?17. Name a tablespace automatically created when you create a database.

http://www.orafaq.com/wiki/ORA-01555

http://www.orafaq.com/wiki/index.php?title=Interview_Questions&action=edit&section=3

http://www.orafaq.com/wiki/ORA-01555




When database is created then system tablespace is created automatically.....

18. When creating a user, what permissions must you grant to allow them to connect to thedatabase?

Grant create session to username;

19. How do you add a data file to a tablespace?

Syntax will be like this:

alter tablespace USERS add datafile '/ora01/oradata/users02.dbf' size 50M;

20. How do you resize a data file?

Alter database datafile '/ora01/oradata/users02.dbf' resize 100M;

21. What view would you use to look at the size of a data file?

dba_data_files

22. What view would you use to determine free space in a tablespace?

DBA_TS_QUOTAS

23. How would you determine who has added a row to a table?

By using trigger on INSERT option

24. How can you rebuild an index?

ALTER INDEX index_name REBUILD;

25. Explain what partitioning is and what its benefit is.

A table partition is also a table segment, and by using partitioning technique

we can enhance performance of table access.

26. You have just compiled a PL/SQL package but got errors, how would you view theerrors?

By using ERRNAME and ERRCODE;

27. How can you gather statistics on a table?28. How can you enable a trace for a session?

alter session set sql_trace='TRUE';

29. What is the difference between the SQL*Loader and IMPORT utilities?



SQL*LOADER loads external data which is in OS files to oracle database tables

while IMPORT utility imports data only which

is exported by EXPORT utility of oracle database.

30. Name two files used for network connection to a database.

TNSNAMES.ORA and SQLNET.ORA

[edit] Oracle Interview Questions1. Describe the difference between a procedure, function and anonymous pl/sql block.Candidate should mention use of DECLARE statement, a function must return a value whilea procedure doesn?t have to.

2. What is a mutating table error and how can you get around it? This happens with triggers.It occurs because the trigger is trying to update a row it is currently using. The usual fix

involves either use of views or temporary tables so the database is selecting from one whileupdating the other.

3. Describe the use of %ROWTYPE and %TYPE in PL/SQL Expectedanswer: %ROWTYPE allows you to associate a variable with an entire table row.The %TYPE associates a variable with a single column type.

4. What packages (if any) has Oracle provided for use by developers? Expected answer:Oracle provides the DBMS_ series of packages. There are many which developers shouldbe aware of such as DBMS_SQL, DBMS_PIPE, DBMS_TRANSACTION, DBMS_LOCK,DBMS_ALERT, DBMS_OUTPUT, DBMS_JOB, DBMS_UTILITY, DBMS_DDL, UTL_FILE. If they can mention a few of these and describe how they used them, even better. If theyinclude the SQL routines provided by Oracle, great, but not really what was asked.

5. Describe the use of PL/SQL tables Expected answer: PL/SQL tables are scalar arraysthat can be referenced by a binary integer. They can be used to hold values for use in later queries or calculations. In Oracle 8 they will be able to be of the %ROWTYPE designation,or RECORD.

6. When is a declare statement needed ? The DECLARE statement is used in PL/SQLanonymous blocks such as with stand alone, non-stored PL/SQL procedures. It must come

first in a PL/SQL stand alone file if it is used.

7. In what order should a open/fetch/loop set of commands in a PL/SQL block beimplemented if you use the %NOTFOUND cursor variable in the exit when statement?Why? Expected answer: OPEN then FETCH then LOOP followed by the exit when. If notspecified in this order will result in the final return being done twice because of the waythe %NOTFOUND is handled by PL/SQL.





6. What is the fastest query method for a tableFetch by rowid

7. Explain the use of TKPROF? What initialization parameter should be turned on to get full

TKPROF output?The tkprof tool is a tuning tool used to determine cpu and execution times for SQLstatements. You use it by first setting timed_statistics to true in the initialization file and thenturning on tracing for either the entire database via the sql_trace parameter or for thesession using the ALTER SESSION command. Once the trace file is generated you run thetkprof tool against the trace file and then look at the output from the tkprof tool. This can alsobe used to generate explain plan output.

8. When looking at v$sysstat you see that sorts (disk) is high. Is this bad or good? If bad-How do you correct it?If you get excessive disk sorts this is bad. This indicates you need to tune the sort area

parameters in the initialization files. The major sort are parameter is the SORT_AREA_SIZeparameter.

9. When should you increase copy latches? What parameters control copy latchesWhen you get excessive contention for the copy latches as shown by the "redo copy" latchhit ratio. You can increase copy latches via the initialization parameter LOG_SIMULTANEOUS_COPIES to twice the number of CPUs on your system.

10. Where can you get a list of all initialization parameters for your instance? How about anindication if they are default settings or have been changed

You can look in the init.ora file for an indication of manually set parameters. For allparameters, their value and whether or not the current value is the default value, look in thev$parameter view.

11. Describe hit ratio as it pertains to the database buffers. What is the difference betweeninstantaneous and cumulative hit ratio and which should be used for tuningThe hit ratio is a measure of how many times the database was able to read a value fromthe buffers verses how many times it had to re-read a data value from the disks. A valuegreater than 80-90% is good, less could indicate problems. If you simply take the ratio of existing parameters this will be a cumulative value since the database started. If you do acomparison between pairs of readings based on some arbitrary time span, this is the

instantaneous ratio for that time span. Generally speaking an instantaneous reading givesmore valuable data since it will tell you what your instance is doing for the time it wasgenerated over.

12. Discuss row chaining, how does it happen? How can you reduce it? How do you correctitRow chaining occurs when a VARCHAR2 value is updated and the length of the new valueis longer than the old value and won?t fit in the remaining block space. This results in the



row chaining to another block. It can be reduced by setting the storage parameters on thetable to appropriate values. It can be corrected by export and import of the effected table.

[edit] Oracle Interview Questions

1. Give one method for transferring a table from one schema to another:There are several possible methods, export-import, CREATE TABLE... AS SELECT, or COPY.

2. What is the purpose of the IMPORT option IGNORE? What is it?s default settingThe IMPORT IGNORE option tells import to ignore "already exists" errors. If it is notspecified the tables that already exist will be skipped. If it is specified, the error is ignoredand the tables data will be inserted. The default value is N.

3. You have a rollback segment in a version 7.2 database that has expanded beyondoptimal, how can it be restored to optimal

Use the ALTER TABLESPACE ..... SHRINK command.

4. If the DEFAULT and TEMPORARY tablespace clauses are left out of a CREATE USERcommand what happens? Is this bad or good? WhyThe user is assigned the SYSTEM tablespace as a default and temporary tablespace. Thisis bad because it causes user objects and temporary segments to be placed into theSYSTEM tablespace resulting in fragmentation and improper table placement (only datadictionary objects and the system rollback segment should be in SYSTEM).

5. What are some of the Oracle provided packages that DBAs should be aware of Oracle provides a number of packages in the form of the DBMS_ packages owned by the

SYS user. The packages used by DBAs may include: DBMS_SHARED_POOL,DBMS_UTILITY, DBMS_SQL, DBMS_DDL, DBMS_SESSION, DBMS_OUTPUT andDBMS_SNAPSHOT. They may also try to answer with the UTL*.SQL or CAT*.SQL series of SQL procedures. These can be viewed as extra credit but aren?t part of the answer.

6. What happens if the constraint name is left out of a constraint clauseThe Oracle system will use the default name of SYS_Cxxxx where xxxx is a systemgenerated number. This is bad since it makes tracking which table the constraint belongs toor what the constraint does harder.

7. What happens if a tablespace clause is left off of a primary key constraint clauseThis results in the index that is automatically generated being placed in then users defaulttablespace. Since this will usually be the same tablespace as the table is being created in,this can cause serious performance problems.

8. What is the proper method for disabling and re-enabling a primary key constraintYou use the ALTER TABLE command for both. However, for the enable clause you mustspecify the USING INDEX and TABLESPACE clause for primary keys.





9. What happens if a primary key constraint is disabled and then enabled without fullyspecifying the index clauseThe index is created in the user?s default tablespace and all sizing information is lost.Oracle doesn?t store this information as a part of the constraint definition, but only as part of

the index definition, when the constraint was disabled the index was dropped and theinformation is gone.

10. (On UNIX) When should more than one DB writer process be used? How many shouldbe usedIf the UNIX system being used is capable of asynchronous IO then only one is required, if the system is not capable of asynchronous IO then up to twice the number of disks used byOracle number of DB writers should be specified by use of the db_writers initializationparameter.

11. You are using hot backup without being in archivelog mode, can you recover in the

event of a failure? Why or why notYou can?t use hot backup without being in archivelog mode. So no, you couldn?t recover.

12. What causes the "snapshot too old" error? How can this be prevented or mitigatedThis is caused by large or long running transactions that have either wrapped onto their ownrollback space or have had another transaction write on part of their rollback space. Thiscan be prevented or mitigated by breaking the transaction into a set of smaller transactionsor increasing the size of the rollback segments and their extents.

13. How can you tell if a database object is invalid By checking the status column of the

DBA_, ALL_ or USER_OBJECTS views, depending upon whether you own or only havepermission on the view or are using a DBA account.

13. A user is getting an ORA-00942 error yet you know you have granted them permissionon the table, what else should you checkYou need to check that the user has specified the full name of the object (select empid fromscott.emp; instead of select empid from emp;) or has a synonym that balls to the object(create synonym emp for scott.emp;)

14. A developer is trying to create a view and the database won?t let him. He has the"DEVELOPER" role which has the "CREATE VIEW" system privilege and SELECT grants

on the tables he is using, what is the problemYou need to verify the developer has direct grants on all tables used in the view. You can?tcreate a stored object with grants given through views.

15. If you have an example table, what is the best way to get sizing data for the productiontable implementationThe best way is to analyze the table and then use the data provided in the DBA_TABLESview to get the average row length and other pertinent data for the calculation. The quick



and dirty way is to look at the number of blocks the table is actually using and ratio thenumber of rows in the table to its number of blocks against the number of expected rows.

16. How can you find out how many users are currently logged into the database? How canyou find their operating system id

There are several ways. One is to look at the v$session or v$process views. Another way isto check the current_logins parameter in the v$sysstat view. Another if you are on UNIX is todo a "ps -ef|grep oracle|wc -l? command, but this only works against a single instanceinstallation.

17. A user selects from a sequence and gets back two values, his select is: SELECTpk_seq.nextval FROM dual;What is the problem Somehow two values have been insertedinto the dual table. This table is a single row, single column table that should only have onevalue in it.

18. How can you determine if an index needs to be dropped and rebuilt

Run the ANALYZE INDEX command on the index to validate its structure and then calculatethe ratio of LF_BLK_LEN/LF_BLK_LEN+BR_BLK_LEN and if it isn?t near 1.0 (i.e. greater than 0.7 or so) then the index should be rebuilt. Or if the ratio BR_BLK_LEN/LF_BLK_LEN+BR_BLK_LEN is nearing 0.3.

[edit] Oracle Interview Questions1. How can variables be passed to a SQL routineBy use of the & symbol. For passing in variables the numbers 1-8 can be used (&1,&2,...,&8) to pass the values after the command into the SQLPLUS session. To be promptedfor a specific variable, place the ampersanded variable in the code itself: "select * from

dba_tables where owner=&owner_name;" . Use of double ampersands tells SQLPLUS toresubstitute the value for each subsequent use of the variable, a single ampersand willcause a reprompt for the value unless an ACCEPT statement is used to get the value fromthe user.

2. You want to include a carriage return/linefeed in your output from a SQL script, how canyou do thisThe best method is to use the CHR() function (CHR(10) is a return/linefeed) and theconcatenation function "||". Another method, although it is hard to document and isn?talways portable is to use the return/linefeed as a part of a quoted string.

3. How can you call a PL/SQL procedure from SQLBy use of the EXECUTE (short form EXEC) command.

4. How do you execute a host operating system command from within SQLBy use of the exclamation ball "!" (in UNIX and some other OS) or the HOST (HO)command.





5. You want to use SQL to build SQL, what is this called and give an exampleThis is called dynamic SQL. An example would be: set lines 90 pages 0 termout off feedback off verify off spool drop_all.sql select ?drop user ?||username||? cascade;? fromdba_users where username not in ("SYS?,?SYSTEM?); spool off Essentially you are

looking to see that they know to include a command (in this case DROPUSER...CASCADE;) and that you need to concatenate using the ?||? the values selectedfrom the database.

6. What SQLPlus command is used to format output from a selectThis is best done with the COLUMN command.

7. You want to group the following set of select returns, what can you group onMax(sum_of_cost), min(sum_of_cost), count(item_no), item_no The only column that canbe grouped on is the "item_no" column, the rest have aggregate functions associated withthem.

8. What special Oracle feature allows you to specify how the cost based system treats aSQL statementThe COST based system allows the use of HINTs to control the optimizer path selection. If they can give some example hints such as FIRST ROWS, ALL ROWS, USING INDEX,STAR, even better.

9. You want to determine the location of identical rows in a table before attempting to placea unique index on the table, how can this be doneOracle tables always have one guaranteed unique column, the rowid column. If you use a

min/max function against your rowid and then select against the proposed primary key youcan squeeze out the rowids of the duplicate rows pretty quick. For example: select rowidfrom emp e where e.rowid > (select min(x.rowid) from emp x where x.emp_no = e.emp_no);In the situation where multiple columns make up the proposed key, they must all be used inthe where clause.

10. What is a Cartesian productA Cartesian product is the result of an unrestricted join of two or more tables. The result setof a three table Cartesian product will have x * y * z number of rows where x, y, zcorrespond to the number of rows in each table involved in the join.

11. You are joining a local and a remote table, the network manager complains about thetraffic involved, how can you reduce the network traffic Push the processing of the remotedata to the remote instance by using a view to pre-select the information for the join. Thiswill result in only the data required for the join being sent across.

11. What is the default ordering of an ORDER BY clause in a SELECT statementAscending



12. What is tkprof and how is it usedThe tkprof tool is a tuning tool used to determine cpu and execution times for SQLstatements. You use it by first setting timed_statistics to true in the initialization file and thenturning on tracing for either the entire database via the sql_trace parameter or for the

session using the ALTER SESSION command. Once the trace file is generated you run thetkprof tool against the trace file and then look at the output from the tkprof tool. This can alsobe used to generate explain plan output.

13. What is explain plan and how is it usedThe EXPLAIN PLAN command is a tool to tune SQL statements. To use it you must have anexplain_table generated in the user you are running the explain plan for. This is createdusing the utlxplan.sql script. Once the explain plan table exists you run the explain plancommand giving as its argument the SQL statement to be explained. The explain_plan tableis then queried to see the execution plan of the statement. Explain plans can also be runusing tkprof.

14. How do you set the number of lines on a page of output? The widthThe SET command in SQLPLUS is used to control the number of lines generated per pageand the width of those lines, for example SET PAGESIZE 60 LINESIZE 80 will generatereports that are 60 lines long with a line width of 80 characters. The PAGESIZE andLINESIZE options can be shortened to PAGES and LINES.

15. How do you prevent output from coming to the screenThe SET option TERMOUT controls output to the screen. Setting TERMOUT OFF turns off screen output. This option can be shortened to TERM.

16. How do you prevent Oracle from giving you informational messages during and after aSQL statement executionThe SET options FEEDBACK and VERIFY can be set to OFF.

17. How do you generate file output from SQLBy use of the SPOOL comm

[edit] Oracle Interview Questions1. What is a CO-RELATED SUBQUERY

A CO-RELATED SUBQUERY is one that has a correlation name as table or view designator in the FROM clause of the outer query and the same correlation name as a qualifier of asearch condition in the WHERE clause of the subquery. eg

SELECT field1 from table1 X

WHERE field2>(select avg(field2) from table1 Y

where

field1=X.field1);





(The subquery in a correlated subquery is revaluated for every row of the table or viewnamed in the outer query.)2. What are various joins used while writing SUBQUERIESSelf join-Its a join foreign key of a table references the same table.

Outer Join--Its a join condition used where One can query all the rows of one of the tables inthe join condition even though they don't satisfy the join condition.Equi-join--Its a join condition that retrieves rows from one or more tables in which one or more columns in one table are equal to one or more columns in the second table.3. What are various constraints used in SQLNULL NOT NULL CHECK DEFAULT4. What are different Oracle database objectsTABLES VIEWS INDEXES SYNONYMS SEQUENCES TABLESPACES etc5. What is difference between Rename and AliasRename is a permanent name given to a table or column whereas Alias is a temporaryname given to a table or column which do not exist once the SQL statement is executed.

6. What is a viewA view is stored procedure based on one or more tables, its a virtual table.7. What are various privileges that a user can grant to another user SELECT CONNECT RESOURCE8. What is difference between UNIQUE and PRIMARY KEY constraintsA table can have only one PRIMARY KEY whereas there can be any number of UNIQUEkeys. The columns that compose PK are automatically define NOT NULL, whereas acolumn that compose a UNIQUE is not automatically defined to be mandatory must alsospecify the column is NOT NULL.9. Can a primary key contain more than one columns

Yes10. How you will avoid duplicating records in a queryBy using DISTINCT11. What is difference between SQL and SQL*PLUSSQL*PLUS is a command line tool where as SQL and PL/SQL language interface andreporting tool. Its a command line tool that allows user to type SQL commands to beexecuted directly against an Oracle database. SQL is a language used to query therelational database(DML,DCL,DDL). SQL*PLUS commands are used to format query result,Set options, Edit SQL commands and PL/SQL.12. Which datatype is used for storing graphics and imagesLONG RAW data type is used for storing BLOB's (binary large objects).

13. How will you delete duplicating rows from a base tableDELETE FROM table_name A WHERE rowid>(SELECT min(rowid) from table_name Bwhere B.table_no=A.table_no);CREATE TABLE new_table AS SELECT DISTINCT * FROM old_table;DROP old_table RENAME new_table TO old_table DELETE FROM table_name A WHERErowid NOT IN (SELECT MAX(ROWID) FROM table_name GROUP BY column_name)

14. What is difference between SUBSTR and INSTR



SUBSTR returns a specified portion of a string eg SUBSTR('BCDEF',4) output BCDE INSTRprovides character position in which a pattern is found in a string.eg INSTR('ABC-DC-F','-',2) output 7 (2nd occurence of '-')15. There is a string '120000 12 0 .125' ,how you will find the position of the decimal placeINSTR('120000 12 0 .125',1,'.') output 13

16. There is a '%' sign in one field of a column. What will be the query to find it.'\' Should be used before '%'.17. When you use WHERE clause and when you use HAVING clauseHAVING clause is used when you want to specify a condition for a group function and it iswritten after GROUP BY clause The WHERE clause is used when you want to specify acondition for columns, single row functions except group functions and it is written beforeGROUP BY clause if it is used.18. Which is more faster - IN or EXISTSEXISTS is more faster than IN because EXISTS returns a Boolean value whereas IN returnsa value.19. What is a OUTER JOIN

Outer Join--Its a join condition used where you can query all the rows of one of the tables inthe join condition even though they dont satisfy the join condition.20. How you will avoid your query from using indexesSELECT * FROM emp Where emp_no+' '=12345;i.e you have to concatenate the column name with space within codes in the wherecondition.SELECT /*+ FULL(a) */ ename, emp_no from emp where emp_no=1234;i.e using HINTS

[edit] Oracle Interview Questions1. What is a pseudo column. Give some examplesIt is a column that is not an actual column in the table.eg USER, UID, SYSDATE, ROWNUM, ROWID, NULL, AND LEVEL.Suppose customer table is there having different columns like customer no, payments.Whatwill be the query to select top three max payments.For top N queries, seehttp://www.orafaq.com/forum/mv/msg/160920/472554/102589/#msg_472554 post2. What is the purpose of a cluster.Oracle does not allow a user to specifically locate tables, since that is a part of the functionof the RDBMS. However, for the purpose of increasing performance, oracle allows a

developer to create a CLUSTER. A CLUSTER provides a means for storing data fromdifferent tables together for faster retrieval than if the table placement were left to theRDBMS.3. What is a cursor.Oracle uses work area to execute SQL statements and store processing informationPL/SQL construct called a cursor lets you name a work area and access its storedinformation A cursor is a mechanism used to fetch more than one row in a Pl/SQl block.4. Difference between an implicit & an explicit cursor.


http://www.orafaq.com/forum/mv/msg/160920/472554/102589/#msg_472554


http://www.orafaq.com/forum/mv/msg/160920/472554/102589/#msg_472554



The return type for a cursor must be a record type.It can be declared explicitly as a user-defined or %ROWTYPE can be used. eg TYPE t_studentsref IS REF CURSOR RETURNstudents%ROWTYPE12. How you open and close a cursor variable.Why it is required.OPEN cursor variable FOR SELECT...Statement CLOSE cursor variable In order to

associate a cursor variable with a particular SELECT statement OPEN syntax is used.Inorder to free the resources used for the query CLOSE statement is used.13. How you were passing cursor variables in PL/SQL 2.2.In PL/SQL 2.2 cursor variables cannot be declared in a package.This is because the storagefor a cursor variable has to be allocated using Pro*C or OCI with version 2.2,the only meansof passing a cursor variable to a PL/SQL block is via bind variable or a procedureparameter.14. Can cursor variables be stored in PL/SQL tables.If yes how.If not why.No, a cursor variable points a row which cannot be stored in a two-dimensional PL/SQLtable.15. Difference between procedure and function.

Functions are named PL/SQL blocks that return a value and can be called with argumentsprocedure a named block that can be called with parameter. A procedure all is a PL/SQLstatement by itself, while a Function call is called as part of an expression.16. What are different modes of parameters used in functions and procedures.IN OUT INOUT17. What is difference between a formal and an actual parameter The variables declared in the procedure and which are passed, as arguments are calledactual, the parameters in the procedure declaration. Actual parameters contain the valuesthat are passed to a procedure and receive results. Formal parameters are the placeholdersfor the values of actual parameters

18. Can the default values be assigned to actual parameters.Yes19. Can a function take OUT parameters.If not why.Yes. A function return a value, but can also have one or more OUT parameters. it is bestpractice, however to use a procedure rather than a function if you have multiple values toreturn.20. What is syntax for dropping a procedure and a function .Are these operations possible.

Drop Procedure procedure_name

Drop Function function_name

21. What are ORACLE PRECOMPILERS.Using ORACLE PRECOMPILERS ,SQL statements and PL/SQL blocks can be containedinside 3GL programs written in C,C++,COBOL,PASCAL, FORTRAN,PL/1 AND ADA. ThePrecompilers are known as Pro*C,Pro*Cobol,... This form of PL/SQL is known as embeddedpl/sql,the language in which pl/sql is embedded is known as the host language. Theprcompiler translates the embedded SQL and pl/sql ststements into calls to the precompiler



runtime library.The output must be compiled and linked with this library to creater anexecutable.22. What is OCI. What are its uses.Oracle Call Interface is a method of accesing database from a 3GL program. Uses--Noprecompiler is required,PL/SQL blocks are executed like other DML statements.

The OCI library provides

-functions to parse SQL statemets

-bind input variables

-bind output variables

-execute statements

-fetch the results

23. Difference between database triggers and form triggers.a) Data base trigger(DBT) fires when a DML operation is performed on a data basetable.Form trigger(FT) Fires when user presses a key or navigates between fields on thescreen b) Can be row level or statement level No distinction between row level andstatement level. c) Can manipulate data stored in Oracle tables via SQL Can manipulatedata in Oracle tables as well as variables in forms. d) Can be fired from any sessionexecuting the triggering DML statements. Can be fired only from the form that define thetrigger. e) Can cause other database triggers to fire.Can cause other database triggers tofire,but not other form triggers.24. What is an UTL_FILE.What are different procedures and functions associatedwith it. UTL_FILE is a package that adds the ability to read and write to operating systemfiles Procedures associated with it are FCLOSE, FCLOSE_ALL and 5 procedures to outputdata to a file PUT, PUT_LINE, NEW_LINE, PUTF, FFLUSH.PUT,

FFLUSH.PUT_LINE,FFLUSH.NEW_LINE. Functions associated with it are FOPEN,ISOPEN.25. Can you use a commit statement within a database trigger.No26. What is the maximum buffer size that can be specified using theDBMS_OUTPUT.ENABLE function?1,000,000

[edit] Oracle Interview Questions1. When looking at the estat events report you see that you are getting busy buffer waits. Isthis bad? How can you find what is causing it

Buffer busy waits could indicate contention in redo, rollback or data blocks. You need tocheck the v$waitstat view to see what areas are causing the problem. The value of the"count" column tells where the problem is, the "class" column tells you with what. UNDO isrollback segments, DATA is data base buffers.

2. If you see contention for library caches how can you fix itIncrease the size of the shared pool.





A large number of small shrinks indicates a need to increase the size of the rollbacksegment extents. Ideally you should have no shrinks or a small number of large shrinks. Tofix this just increase the size of the extents and adjust optimal accordingly.

12. You look at the dba_rollback_segs view and see that you have a large number of wraps

is this a problemA large number of wraps indicates that your extent size for your rollback segments areprobably too small. Increase the size of your extents to reduce the number of wraps. Youcan look at the average transaction size in the same view to get the information ontransaction size.

[edit] Oracle Interview Questions1. You have just started a new instance with a large SGA on a busy existing server.Performance is terrible, what should you check for The first thing to check with a large SGA is that it isn?t being swapped out.

2. What OS user should be used for the first part of an Oracle installation (on UNIX)You must use root first.

3. When should the default values for Oracle initialization parameters be used as isNever

4. How many control files should you have? Where should they be locatedAt least 2 on separate disk spindles. Be sure they say on separate disks, not just filesystems.

5. How many redo logs should you have and how should they be configured for maximumrecoverabilityYou should have at least three groups of two redo logs with the two logs each on a separatedisk spindle (mirrored by Oracle). The redo logs should not be on raw devices on UNIX if itcan be avoided.

6. You have a simple application with no "hot" tables (i.e. uniform IO and accessrequirements). How many disks should you have assuming standard layout for SYSTEM,USER, TEMP and ROLLBACK tablespacesAt least 7, see disk configuration answer above.

7. Describe third normal formSomething like: In third normal form all attributes in an entity are related to the primary keyand only to the primary key

8. Is the following statement true or false:"All relational databases must be in third normal form" False. While 3NF is good for logicaldesign most databases, if they have more than just a few tables, will not perform well using





full 3NF. Usually some entities will be denormalized in the logical to physical transfer process.

9. What is an ERDAn ERD is an Entity-Relationship-Diagram. It is used to show the entities and relationships

for a database logical model.

10. Why are recursive relationships bad? How do you resolve themA recursive relationship (one where a table relates to itself) is bad when it is a hardrelationship (i.e. neither side is a "may" both are "must") as this can result in it not beingpossible to put in a top or perhaps a bottom of the table (for example in the EMPLOYEEtable you couldn?t put in the PRESIDENT of the company because he has no boss, or the

junior janitor because he has no subordinates). These type of relationships are usuallyresolved by adding a small intersection entity.

11. What does a hard one-to-one relationship mean (one where the relationship on both

ends is "must")Expected answer: This means the two entities should probably be made into one entity.

12. How should a many-to-many relationship be handledBy adding an intersection entity table

13. What is an artificial (derived) primary key? When should an artificial (or derived) primarykey be usedA derived key comes from a sequence. Usually it is used when a concatenated keybecomes too cumbersome to use as a foreign key.

[edit] Oracle Interview Questions1. When should you consider denormalizationWhenever performance analysis indicates it would be beneficial to do so withoutcompromising data integrity.

2. How can you determine if an Oracle instance is up from the operating system levelThere are several base Oracle processes that will be running on multi-user operatingsystems, these will be smon, pmon, dbwr and lgwr. Any answer that has them using their operating system process showing feature to check for these is acceptable. For example, on

UNIX a ps -ef|grep dbwr will show what instances are up.

3. Users from the PC clients are getting messages indicating : ORA-06114: (Cnct err, can'tget err txt. See Servr Msgs & Codes Manual)

What could the problem be The instance name is probably incorrect in their connectionstring.





4. Users from the PC clients are getting the following error stack: ERROR: ORA-01034:ORACLE not available ORA-07318: smsget: open error when opening sgadef.dbf file. HP-UX Error: 2: No such file or directory

What is the probable cause The Oracle instance is shutdown that they are trying to access,restart the instance.

5. How can you determine if the SQLNET process is running for SQLNET V1? How aboutV2For SQLNET V1 check for the existence of the orasrv process. You can use the command"tcpctl status" to get a full status of the V1 TCPIP server, other protocols have similar command formats. For SQLNET V2 check for the presence of the LISTENER process(s) or you can issue the command "lsnrctl status".

6. What file will give you Oracle instance status information? Where is it located

The alert.ora log. It is located in the directory specified by the background_dump_destparameter in the v$parameter table.

7. Users aren?t being allowed on the system. The following message is received: ORA-00257 archiver is stuck. Connect internal only, until freed What is the problem The archivedestination is probably full, backup the archive logs and remove them and the archiver willre-start.

8. Where would you look to find out if a redo log was corrupted assuming you are usingOracle mirrored redo logs

There is no message that comes to the SQLDBA or SRVMGR programs during startup inthis situation, you must check the alert.log file for this information.

9. You attempt to add a datafile and get: ORA-01118: cannot add anymore datafiles: limit of 40 exceeded What is the problem and how can you fix it When the database was createdthe db_files parameter in the initialization file was set to 40. You can shutdown and resetthis to a higher value, up to the value of MAX_DATAFILES as specified at databasecreation. If the MAX_DATAFILES is set to low, you will have to rebuild the control file toincrease it before proceeding.

10. You look at your fragmentation report and see that smon hasn?t coalesced any of you

tablespaces, even though you know several have large chunks of contiguous free extents.What is the problem

Check the dba_tablespaces view for the value of pct_increase for the tablespaces. If pct_increase is zero, smon will not coalesce their free space.

11. Your users get the following error: ORA-00055 maximum number of DML locksexceeded What is the problem and how do you fix it The number of DML Locks is set by the



initialization parameter DML_LOCKS. If this value is set to low (which it is by default) youwill get this error. Increase the value of DML_LOCKS. If you are sure that this is just atemporary problem, you can have them wait and then try again later and the error shouldclear.

12. You get a call from you backup DBA while you are on vacation. He has corrupted all of the control files while playing with the ALTER DATABASE BACKUP CONTROLFILEcommand. What do you doAs long as all datafiles are safe and he was successful with the BACKUP controlfilecommand you can do the following: CONNECT INTERNAL STARTUP MOUNT (Take anyread-only tablespaces offline before next step ALTER DATABASE DATAFILE .... OFFLINE;)RECOVER DATABASE USING BACKUP CONTROLFILE ALTER DATABASE OPENRESETLOGS; (bring read-only tablespaces back online) Shutdown and backup the system,then restart If they have a recent output file from the ALTER DATABASE BACKUPCONTROL FILE TO TRACE; command, they can use that to recover as well. If no backupof the control file is available then the following will be required: CONNECT INTERNAL

STARTUP NOMOUNT CREATE CONTROL FILE .....; However, they will need to know all of the datafiles, logfiles, and settings for MAXLOGFILES, MAXLOGMEMBERS,MAXLOGHISTORY, MAXDATAFILES for the database to use the command.

[edit] Oracle Interview Questions1. How would you determine the time zone under which a database was operating? 2.Explain the use of setting GLOBAL_NAMES equal to TRUE. 3. What command would youuse to encrypt a PL/SQL application? 4. Explain the difference between a FUNCTION,PROCEDURE and PACKAGE. 5. Explain the use of table functions. 6. Name three advisorystatistics you can collect. 7. Where in the Oracle directory tree structure are audit traces

placed? 8. Explain materialized views and how they are used. 9. When a user process fails,what background process cleans up after it? 10. What background process refreshesmaterialized views? 11. How would you determine what sessions are connected and whatresources they are waiting for? 12. Describe what redo logs are. 13. How would you force alog switch? 14. Give two methods you could use to determine what DDL changes have beenmade. 15. What does coalescing a tablespace do? 16. What is the difference between aTEMPORARY tablespace and a PERMANENT tablespace? 17. Name a tablespaceautomatically created when you create a database. 18. When creating a user, whatpermissions must you grant to allow them to connect to the database? 19. How do you adda data file to a tablespace? 20. How do you resize a data file? 21. What view would you use

to look at the size of a data file? 22. What view would you use to determine free space in atablespace? 23. How would you determine who has added a row to a table? 24. How canyou rebuild an index? 25. Explain what partitioning is and what its benefit is. 26. You have

just compiled a PL/SQL package but got errors, how would you view the errors? 27. Howcan you gather statistics on a table? 28. How can you enable a trace for a session? 29.What is the difference between the SQL*Loader and IMPORT utilities? 30. Name two filesused for network connection to a database.





[edit] Oracle Interview Questions1. In a system with an average of 40 concurrent users you get the following from a query onrollback extents:

ROLLBACK CUR EXTENTS

--------------------------R01 11 R02 8 R03 12 R04 9 SYSTEM 4 2. You have room for each to grow by 20 moreextents each. Is there a problem? Should you take any actionNo there is not a problem. You have 40 extents showing and an average of 40 concurrentusers. Since there is plenty of room to grow no action is needed.

3. You see multiple extents in the temporary tablespace. Is this a problemAs long as they are all the same size this isn?t a problem. In fact, it can even improveperformance since Oracle won?t have to create a new extent when a user needs one.

4. Define OFA.OFA stands for Optimal Flexible Architecture. It is a method of placing directories and files inan Oracle system so that you get the maximum flexibility for future tuning and fileplacement.

5. How do you set up your tablespace on installationThe answer here should show an understanding of separation of redo and rollback, dataand indexes and isolation os SYSTEM tables from other tables. An example would be tospecify that at least 7 disks should be used for an Oracle installation so that you can place

SYSTEM tablespace on one, redo logs on two (mirrored redo logs) the TEMPORARYtablespace on another, ROLLBACK tablespace on another and still have two for DATA andINDEXES. They should indicate how they will handle archive logs and exports as well. Aslong as they have a logical plan for combining or further separation more or less disks canbe specified.

6. What should be done prior to installing Oracle (for the OS and the disks)adjust kernel parameters or OS tuning parameters in accordance with installation guide. Besure enough contiguous disk space is available.

7. You have installed Oracle and you are now setting up the actual instance. You have been

waiting an hour for the initialization script to finish, what should you check first to determineif there is a problemCheck to make sure that the archiver isn?t stuck. If archive logging is turned on during installa large number of logs will be created. This can fill up your archive log destination causingOracle to stop to wait for more space.

8. When configuring SQLNET on the server what files must be set up





INITIALIZATION file, TNSNAMES.ORA file, SQLNET.ORA file

9. When configuring SQLNET on the client what files need to be set upSQLNET.ORA, TNSNAMES.ORA

10. What must be installed with ODBC on the client in order for it to work with OracleSQLNET and PROTOCOL (for example: TCPIP adapter) layers of the transport programs.

[edit] General Oracle Questions What Oracle products have you worked with?

What version of Oracle were you running?

Compare Oracle to any other database that you know. Why would you prefer to work on

one and not on the other?

[edit] Oracle DBA Questions

Typical DBA questions: How many databases and what sizes?

Did you use online or off-line backups? Why?

If you have to advise a backup strategy for a new application, how would you approach it

and what questions will you ask?

If a customer calls you about a hanging database session, what will you do to resolve it?

How many control files and redo logs should a database have?

[edit] Oracle Developer QuestionsTypical Developer questions:

Tell us about the projects you've worked on.

What language was the application written in?

What programming languages are you familiar with?

What technologies did you use?

[edit] Technical Oracle QuestionsTo test your technical knowledge, try one of the OraFAQ Quizzes.

Category: Career management



http://www.orafaq.com/wiki/DBA


http://www.orafaq.com/wiki/Developer


http://www.orafaq.com/wiki/Quizzes

http://www.orafaq.com/wiki/Special:Categories

http://www.orafaq.com/wiki/Category:Career_management



http://www.orafaq.com/wiki/DBA


http://www.orafaq.com/wiki/Developer


http://www.orafaq.com/wiki/Quizzes

http://www.orafaq.com/wiki/Special:Categories

http://www.orafaq.com/wiki/Category:Career_management



PL/SQL Questions

. Describe the difference between a procedure, function and anonymous pl/sql block. Level: Low

Expected answer : Candidate should mention use of DECLARE statement, a function must return a value

while a procedure doesn't have to. Also one can use function in Select Sql statement but not procedure.

2. What is a mutating table error and how can you get around it?

Level: Intermediate

Expected answer: This happens with triggers. It occurs because the trigger is trying to update a row it iscurrently using. The usual fix involves either use of views or temporary tables so the database is selectingrom one while updating the other.

3. Describe the use of %ROWTYPE and %TYPE in PL/SQL

Level: Low

Expected answer: %ROWTYPE allows you to associate a variable with an entire table row. The %TYPEassociates a variable with a single column type.

4. What packages (if any) has Oracle provided for use by developers?

Level: Intermediate to high

Expected answer: Oracle provides the DBMS_ series of packages. There are many which developers

should be aware of such as DBMS_SQL, DBMS_PIPE, DBMS_TRANSACTION, DBMS_LOCK,DBMS_ALERT, DBMS_OUTPUT, DBMS_JOB, DBMS_UTILITY, DBMS_DDL, UTL_FILE. If they canmention a few of these and describe how they used them, even better. If they include the SQL routinesprovided by Oracle, great, but not really what was asked.

5. Describe the use of PL/SQL tables

Level: Intermediate

Expected answer: PL/SQL tables are scalar arrays that can be referenced by a binary integer. They can bused to hold values for use in later queries or calculations. In Oracle they will be able to be of the

%ROWTYPE designation, or RECORD.

6. When is a declare statement needed ?

Level: Low

The DECLARE statement is used in PL/SQL anonymous blocks such as with stand alone, non-storedPL/SQL procedures. It must come first in a PL/SQL stand alone file if it is used.

http://it.toolbox.com/wiki/index.php/SQL

http://it.toolbox.com/wiki/index.php/SQL



7. In what order should a open/fetch/loop set of commands in a PL/SQL block be implemented if you use %NOTFOUND cursor variable in the exit when statement? Why?

Level: Intermediate

Expected answer: OPEN then FETCH then LOOP followed by the exit when. If not specified in this order esult in the final return being done twice because of the way the %NOTFOUND is handled by PL/SQL.

8. What are SQLCODE and SQLERRM and why are they important for PL/SQL developers?

Level: Intermediate

Expected answer: SQLCODE returns the value of the error number for the last error encountered. TheSQLERRM returns the actual error message for the last error encountered. They can be used in exceptiohandling to report, or, store in an error log table, the error that occurred in the code. These are especiallyuseful for the WHEN OTHERS exception.

9. How can you find within a PL/SQL block, if a cursor is open?

Level: Low

Expected answer: Use the %ISOPEN cursor status variable.

0. How can you generate debugging output from PL/SQL?

Level:Intermediate to high

Expected answer: Use the DBMS_OUTPUT package. The DBMS_OUTPUT package can be used to shontermediate results from loops and the status of variables as the procedure is executed, however outputonly occurs after processing is finished, which might not be useful if processing takes a long time. Thepackage UTL_FILE can be used to write to a file, but one must have write access to the output directory. hird possibility is to create a log table and have the procedure write to the table. This will give you

debugging information in real time.

1. What are the types of triggers?

Level:Intermediate to high

Expected Answer: There are 12 types of triggers in PL/SQL that consist of combinations of the BEFORE,AFTER, ROW, TABLE, INSERT, UPDATE, DELETE and ALL key words: BEFORE ALL ROW INSERTAFTER ALL ROW INSERT BEFORE INSERT AFTER INSERT etc.



Level: Low

Expected answer: The Oracle system will use the default name of SYS_Cxxxx where xxxx is a systemgenerated number. This is bad since it makes tracking which table the constraint belongs to or what theconstraint does harder.

7. What happens if a tablespace clause is left off of a primary key constraint clause?

Level: Low

Expected answer: This results in the index that is automatically generated being placed in then users defaablespace. Since this will usually be the same tablespace as the table is being created in, this can cause

serious performance problems.

8. What is the proper method for disabling and re-enabling a primary key constraint?

Level: Intermediate

Expected answer: You use the ALTER TABLE command for both. However, for the enable clause you mspecify the USING INDEX and TABLESPACE clause for primary keys.

9. What happens if a primary key constraint is disabled and then enabled without fully specifying the indexclause?

Level: Intermediate

Expected answer: The index is created in the user?s default tablespace and all sizing information is lost.

Oracle doesn?t store this information as a part of the constraint definition, but only as part of the indexdefinition, when the constraint was disabled the index was dropped and the information is gone.

0. (On UNIX) When should more than one DB writer process be used? How many should be used?

Level: High

Expected answer: If the UNIX system being used is capable of asynchronous IO then only one is requiredhe system is not capable of asynchronous IO then up to twice the number of disks used by Oracle numb

of DB writers should be specified by use of the db_writers initialization parameter.

1. You are using hot backup without being in archivelog mode, can you recover in the event of a failure?Why or why not?

Level: High

Expected answer: You can't use hot backup without being in archivelog mode. So no, you couldn't recove

2. What causes the "snapshot too old" error? How can this be prevented or mitigated?

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http://it.toolbox.com/wiki/index.php/Database

http://it.toolbox.com/wiki/index.php/UNIX



Level: Intermediate

Expected answer: This is caused by large or long running transactions that have either wrapped onto theown rollback space or have had another transaction write on part of their rollback space. This can beprevented or mitigated by breaking the transaction into a set of smaller transactions or increasing the size

he rollback segments and their extents.

3. How can you tell if a database object is invalid?

Level: Low

Expected answer: By checking the STATUS column of the DBA_, ALL_ or USER_OBJECTS views,depending upon whether you own or only have permission on the view or are using a DBA account.

4. A user is getting an ORA-00942 error yet you know you have granted them permission on the table,what else should you check?

Level: Low

Expected answer: You need to check that the user has specified the full name of the object (SELECT emFROM scott.emp; instead of SELECT empid FROM emp;) or has a synonym that points to the objectCREATE SYNONYM emp FOR scott.emp;)

5. A developer is trying to create a view and the database won?t let him. He has the "DEVELOPER" rolewhich has the "CREATE VIEW" system privilege and SELECT grants on the tables he is using, what is thproblem? Level: Intermediate Expected answer: You need to verify the developer has direct grants on allables used in the view. You can't create a stored object with grants given through a role.

6. If you have an example table, what is the best way to get sizing data for the production tablemplementation?

Level: Intermediate

Expected answer: The best way is to analyze the table and then use the data provided in the DBA_TABLview to get the average row length and other pertinent data for the calculation. The quick and dirty way is ook at the number of blocks the table is actually using and ratio the number of rows in the table to itsnumber of blocks against the number of expected rows.

7. How can you find out how many users are currently logged into the database? How can you find their operating system id?

Level: high Expected answer: There are several ways. One is to look at the v$session or v$process viewsAnother way is to check the current_logins parameter in the v$sysstat view. Another if you are on UNIX isdo a "ps -ef|grep oracle|wc -l? command, but this only works against a single instance installation.

8. A user selects from a sequence and gets back two values, his select is:



Expected answer: By use of the exclamation point "!" (in UNIX and some other OS) or the HOST (HO)command.

5. You want to use SQL to build SQL, what is this called and give an example


Expected answer: This is called dynamic SQL. An example would be: set lines 90 pages 0 termout off eedback off verify off spool drop_all.sql select ?drop user ?||username||? cascade;? from dba_users whe

username not in ('SYS','SYSTEM'); spool off Essentially you are looking to see that they know to include acommand (in this case DROP USER...CASCADE;) and that you need to concatenate using the ?||? thevalues selected from the database.

Alternately, if you are using PL/SQL, you can do ls_sql_string := 'CREATE TABLE FRED AS SELECTSYSDATE A_DATE FROM DUAL'; EXECUTE IMMEDIATE ls_sql_string;

6. What SQLPlus command is used to format output from a select?

Level: low

Expected answer: This is best done with the COLUMN command.

7. You want to group the following set of select returns, what can you group on? Max(sum_of_cost),min(sum_of_cost), count(item_no), item_no Level: Intermediate Expected answer: The only column that cbe grouped on is the "item_no" column, the rest have aggregate functions associated with them.

8. What special Oracle feature allows you to specify how the cost based system treats a SQL statement?

Level: Intermediate to high Expected answer: The COST based system allows the use of HINTs to controhe optimizer path selection. If they can give some example hints such as FIRST ROWS, ALL ROWS,

USING INDEX, STAR, even better.

9. You want to determine the location of identical rows in a table before attempting to place a unique indeon the table, how can this be done?

Level: High

Expected answer: Oracle tables always have one guaranteed unique column, the rowid column. If you usmin/max function against your rowid and then select against the proposed primary key you can squeeze ohe rowids of the duplicate rows pretty quick. For example: select rowid from emp e where e.rowid > (sele

min(x.rowid) from emp x where x.emp_no = e.emp_no); In the situation where multiple columns make up proposed key, they must all be used in the where clause.

0. What is a Cartesian product?



Level: Low

Expected answer: A Cartesian product is the result of an unrestricted join of two or more tables. The resuset of a three table Cartesian product will have x * y * z number of rows where x, y, z correspond to thenumber of rows in each table involved in the join.

1. You are joining a local and a remote table, the network manager complains about the traffic involved,how can you reduce the network traffic?

Level: High

Expected answer: Push the processing of the remote data to the remote instance by using a view to pre-select the information for the join. This will result in only the data required for the join being sent across.

2. What is the default ordering of an ORDER BY clause in a SELECT statement?

Level: Low

Expected answer: Ascending

3. What is tkprof and how is it used?

Level: Intermediate to high Expected answer: The tkprof tool is a tuning tool used to determine cpu andexecution times for SQL statements. You use it by first setting timed_statistics to true in the initialization fand then turning on tracing for either the entire database via the sql_trace parameter or for the session ushe ALTER SESSION command. Once the trace file is generated you run the tkprof tool against the trace

and then look at the output from the tkprof tool. This can also be used to generate explain plan output.

4. What is explain plan and how is it used?


Expected answer: The EXPLAIN PLAN command is a tool to tune SQL statements. To use it you must haan explain_table generated in the user you are running the explain plan for. This is created using theutlxplan.sql script. Once the explain plan table exists you run the explain plan command giving as itsargument the SQL statement to be explained. The explain_plan table is then queried to see the executionplan of the statement. Explain plans can also be run using tkprof.

5. How do you set the number of lines on a page of output? The width?

Level: Low

Expected answer: The SET command in SQLPLUS is used to control the number of lines generated per page and the width of those lines, for example SET PAGESIZE 60 LINESIZE 80 will generate reports thaare 60 lines long with a line width of 80 characters. The PAGESIZE and LINESIZE options can be shorteno PAGES and LINES.



4. What are some indications that you need to increase the SHARED_POOL_SIZE parameter?

Level: Intermediate

Expected answer: Poor data dictionary or library cache hit ratios, getting error ORA-04031. Another

ndication is steadily decreasing performance with all other tuning parameters the same.

5. What is the general guideline for sizing db_block_size and db_multi_block_read for an application thatdoes many full table scans?

Level: High

Expected answer: Oracle almost always reads in 64k chunks. The two should have a product equal to 64 a multiple of 64.

6. What is the fastest query method for a table?

Level: Intermediate Expected answer: Fetch by rowid

7. Explain the use of TKPROF? What initialization parameter should be turned on to get full TKPROFoutput?

Level: High

Expected answer: The tkprof tool is a tuning tool used to determine cpu and execution times for SQLstatements. You use it by first setting timed_statistics to true in the initialization file and then turning onracing for either the entire database via the sql_trace parameter or for the session using the ALTER

SESSION command. Once the trace file is generated you run the tkprof tool against the trace file and theook at the output from the tkprof tool. This can also be used to generate explain plan output.

8. When looking at v$sysstat you see that sorts (disk) is high. Is this bad or good? If bad -How do youcorrect it?

Level: Intermediate

Expected answer: If you get excessive disk sorts this is bad. This indicates you need to tune the sort areaparameters in the initialization files. The major sort are parameter is the SORT_AREA_SIZe parameter.

9. When should you increase copy latches? What parameters control copy latches? Level: high Expectedanswer: When you get excessive contention for the copy latches as shown by the "redo copy" latch hit ratYou can increase copy latches via the initialization parameter LOG_SIMULTANEOUS_COPIES to twice tnumber of CPUs on your system.

0. Where can you get a list of all initialization parameters for your instance? How about an indication if thare default settings or have been changed?



Level: Low

Expected answer: You can look in the init.ora file for an indication of manually set parameters. For allparameters, their value and whether or not the current value is the default value, look in the v$parameter view.

1. Describe hit ratio as it pertains to the database buffers. What is the difference between instantaneousand cumulative hit ratio and which should be used for tuning?

Level: Intermediate

Expected answer: The hit ratio is a measure of how many times the database was able to read a value frohe buffers verses how many times it had to re-read a data value from the disks. A value greater than 80-

90% is good, less could indicate problems. If you simply take the ratio of existing parameters this will be acumulative value since the database started. If you do a comparison between pairs of readings based onsome arbitrary time span, this is the instantaneous ratio for that time span. Generally speaking an

nstantaneous reading gives more valuable data since it will tell you what your instance is doing for the timt was generated over.

2. Discuss row chaining, how does it happen? How can you reduce it? How do you correct it?

Level: high

Expected answer: Row chaining occurs when a VARCHAR2 value is updated and the length of the newvalue is longer than the old value and won?t fit in the remaining block space. This results in the row chaino another block. It can be reduced by setting the storage parameters on the table to appropriate values. I

can be corrected by export and import of the effected table.

3. When looking at the estat events report you see that you are getting busy buffer waits. Is this bad? Hocan you find what is causing it?

Level: high

Expected answer: Buffer busy waits could indicate contention in redo, rollback or data blocks. You need tcheck the v$waitstat view to see what areas are causing the problem. The value of the "count" column tewhere the problem is, the "class" column tells you with what. UNDO is rollback segments, DATA is database buffers.

4. If you see contention for library caches how can you fix it?

Level: Intermediate

Expected answer: Increase the size of the shared pool.

5. If you see statistics that deal with "undo" what are they really talking about?



21. If you see a pin hit ratio of less than 0.8 in the estat library cache report is this a problem? If so, how dyou fix it?

Level: Intermediate

Expected answer: This indicate that the shared pool may be too small. Increase the shared pool size.

22. If you see the value for reloads is high in the estat library cache report is this a matter for concern?

Level: Intermediate

Expected answer: Yes, you should strive for zero reloads if possible. If you see excessive reloads thenncrease the size of the shared pool.

23. You look at the dba_rollback_segs view and see that there is a large number of shrinks and they are oelatively small size, is this a problem? How can it be fixed if it is a problem?

Level: High

Expected answer: A large number of small shrinks indicates a need to increase the size of the rollbacksegment extents. Ideally you should have no shrinks or a small number of large shrinks. To fix this justncrease the size of the extents and adjust optimal accordingly.

24. You look at the dba_rollback_segs view and see that you have a large number of wraps is this aproblem?

Level: High

Expected answer: A large number of wraps indicates that your extent size for your rollback segments areprobably too small. Increase the size of your extents to reduce the number of wraps. You can look at theaverage transaction size in the same view to get the information on transaction size.

25. In a system with an average of 40 concurrent users you get the following from a query on rollbackextents: ROLLBACK CUR EXTENTS

-------------------------

R01 11 R02 8 R03 12 R04 9 SYSTEM 4 You have room for each to grow by 20 more extents each. Is the

a problem? Should you take any action?

Level: Intermediate

Expected answer: No there is not a problem. You have 40 extents showing and an average of 40 concurrusers. Since there is plenty of room to grow no action is needed.

26. You see multiple extents in the temporary tablespace. Is this a problem?



Level: Intermediate

Expected answer: As long as they are all the same size this isn?t a problem. In fact, it can even improveperformance since Oracle won?t have to create a new extent when a user needs one.

edit]

nstallation/Configuration

. Define OFA.

Level: Low

Expected answer: OFA stands for Optimal Flexible Architecture. It is a method of placing directories andiles in an Oracle system so that you get the maximum flexibility for future tuning and file placement.

2. How do you set up your tablespace on installation? Level: Low

Expected answer: The answer here should show an understanding of separation of redo and rollback, daand indexes and isolation os SYSTEM tables from other tables. An example would be to specify that at le7 disks should be used for an Oracle installation so that you can place SYSTEM tablespace on one, redoogs on two (mirrored redo logs) the TEMPORARY tablespace on another, ROLLBACK tablespace onanother and still have two for DATA and INDEXES. They should indicate how they will handle archive logand exports as well. As long as they have a logical plan for combining or further separation more or lessdisks can be specified.

3. What should be done prior to installing Oracle (for the OS and the disks)?

Level: Low

Expected Answer: adjust kernel parameters or OS tuning parameters in accordance with installation guideBe sure enough contiguous disk space is available.

4. You have installed Oracle and you are now setting up the actual instance. You have been waiting an hoor the initialization script to finish, what should you check first to determine if there is a problem?


Expected Answer: Check to make sure that the archiver isn?t stuck. If archive logging is turned on duringnstall a large number of logs will be created. This can fill up your archive log destination causing Oracle tstop to wait for more space.

5. When configuring SQLNET on the server what files must be set up?

Level: Intermediate

http://it.toolbox.com/wiki/index.php?title=Interview_Questions_with_Answers_for_Oracle%2C_DBA%2C_and_developer_candidates&action=edit&section=7




Expected answer: INITIALIZATION file, TNSNAMES.ORA file, SQLNET.ORA file

6. When configuring SQLNET on the client what files need to be set up?

Level: Intermediate

Expected answer: SQLNET.ORA, TNSNAMES.ORA

7. What must be installed with ODBC on the client in order for it to work with Oracle?

Level: Intermediate

Expected answer: SQLNET and PROTOCOL (for example: TCPIP adapter) layers of the transportprograms.

8. You have just started a new instance with a large SGA on a busy existing server. Performance is terrib

what should you check for?

Level: Intermediate

Expected answer: The first thing to check with a large SGA is that it isn?t being swapped out.

9. What OS user should be used for the first part of an Oracle installation (on UNIX)?

Level: low

Expected answer: You must use root first.

0. When should the default values for Oracle initialization parameters be used as is?

Level: Low

Expected answer: Never

1. How many control files should you have? Where should they be located?

Level: Low

Expected answer: At least 2 on separate disk spindles. Be sure they say on separate disks, not just filesystems.

2. How many redo logs should you have and how should they be configured for maximum recoverability

Level: Intermediate



Expected answer: You should have at least three groups of two redo logs with the two logs each on aseparate disk spindle (mirrored by Oracle). The redo logs should not be on raw devices on UNIX if it can bavoided.

3. You have a simple application with no "hot" tables (i.e. uniform IO and access requirements). How ma

disks should you have assuming standard layout for SYSTEM, USER, TEMP and ROLLBACK tablespace

Expected answer: At least 7, see disk configuration answer above.

edit]

Data Modeler

. Describe third normal form?

Level: Low

Expected answer: Something like: In third normal form all attributes in an entity are related to the primarykey and only to the primary key

2. Is the following statement true or false: "All relational databases must be in third normal form" Why or wnot? Level: Intermediate Expected answer: False. While 3NF is good for logical design most databases, ifhey have more than just a few tables, will not perform well using full 3NF. Usually some entities will be

denormalized in the logical to physical transfer process.

3. What is an ERD? Level: Low Expected answer: An ERD is an Entity-Relationship-Diagram. It is used toshow the entities and relationships for a database logical model.

4. Why are recursive relationships bad? How do you resolve them? Level: Intermediate A recursiveelationship (one where a table relates to itself) is bad when it is a hard relationship (i.e. neither side is amay" both are "must") as this can result in it not being possible to put in a top or perhaps a bottom of theable (for example in the EMPLOYEE table you couldn?t put in the PRESIDENT of the company because

has no boss, or the junior janitor because he has no subordinates). These type of relationships are usualesolved by adding a small intersection entity.

5. What does a hard one-to-one relationship mean (one where the relationship on both ends is "must")?Level: Low to intermediate Expected answer: This means the two entities should probably be made into oentity.

6. How should a many-to-many relationship be handled? Level: Intermediate Expected answer: By addingan intersection entity table

7. What is an artificial (derived) primary key? When should an artificial (or derived) primary key be used?Level: Intermediate Expected answer: A derived key comes from a sequence. Usually it is used when aconcatenated key becomes too cumbersome to use as a foreign key.





8. When should you consider denormalization? Level: Intermediate Expected answer: Whenever performance analysis indicates it would be beneficial to do so without compromising data integrity.

edit]

UNIX

. How can you determine the space left in a file system?

Level: Low Expected answer: There are several commands to do this: du, df, or bdf

2. How can you determine the number of SQLNET users logged in to the UNIX system? Level: IntermediaExpected answer: SQLNET users will show up with a process unique name that begins with oracle, if youa ps -ef|grep oracle|wc -l you can get a count of the number of users.

3. What command is used to type files to the screen? Level: Low Expected answer: cat, more, pg

4. What command is used to remove a file? Level: Low Expected answer: rm

5. Can you remove an open file under UNIX? Level: Low Expected answer: yes

6. How do you create a decision tree in a shell script? Level: intermediate Expected answer: depending oshell, usually a case-esac or an if-endif or fi structure

7. What is the purpose of the grep command? Level: Low Expected answer: grep is a string searchcommand that parses the specified string from the specified file or files

8. The system has a program that always includes the word nocomp in its name, how can you determine number of processes that are using this program? Level: intermediate Expected answer: ps -ef|grepnocomp*|wc -l

9. What is an inode? Level: Intermediate Expected answer: an inode is a file status indicator. It is stored iboth disk and memory and tracts file status. There is one inode for each file on the system.

0. The system administrator tells you that the system hasn?t been rebooted in 6 months, should he beproud of this? Level: High Expected answer: Maybe. Some UNIX systems don?t clean up well after hemselves. Inode problems and dead user processes can accumulate causing possible performance an

corruption problems. Most UNIX systems should have a scheduled periodic reboot so file systems can be

checked and cleaned and dead or zombie processes cleared out.

1. What is redirection and how is it used? Level: Intermediate Expected answer: redirection is the procesby which input or output to or from a process is redirected to another process. This can be done using thepipe symbol "|", the greater than symbol ">" or the "tee" command. This is one of the strengths of UNIXallowing the output from one command to be redirected directly into the input of another command.





2. How can you find dead processes? Level: Intermediate Expected answer: ps -ef|grep zombie -- or -- wd depending on the system.

3. How can you find all the processes on your system? Level: Low Expected answer: Use the ps comma

4. How can you find your id on a system? Level: Low Expected answer: Use the "who am i" command.

5. What is the finger command? Level: Low Expected answer: The finger command uses data in thepasswd file to give information on system users.

6. What is the easiest method to create a file on UNIX? Level: Low Expected answer: Use the touchcommand

7. What does >> do? Level: Intermediate Expected answer: The ">>" redirection symbol appends theoutput from the command specified into the file specified. The file must already have been created.

8. If you aren?t sure what command does a particular UNIX function what is the best way to determine thcommand? Expected answer: The UNIX man -k command will search the man pages for the value specifReview the results from the command to find the command of interest.

edit]

Oracle Troubleshooting

. How can you determine if an Oracle instance is up from the operating system level? Level: Low Expectanswer: There are several base Oracle processes that will be running on multi-user operating systems,hese will be smon, pmon, dbwr and lgwr. Any answer that has them using their operating system process

showing feature to check for these is acceptable. For example, on UNIX a ps -ef|grep pmon will show whanstances are up.

2. Users from the PC clients are getting messages indicating : Level: Low ORA-06114: (Cnct err, can't geerr txt. See Servr Msgs & Codes Manual) What could the problem be? Expected answer: The instancename is probably incorrect in their connection string.

3. Users from the PC clients are getting the following error stack: Level: Low ERROR: ORA-01034:ORACLE not available ORA-07318: smsget: open error when opening sgadef.dbf file. HP-UX Error: 2: Nosuch file or directory What is the probable cause? Expected answer: The Oracle instance is shutdown thahey are trying to access, restart the instance.

4. How can you determine if the SQLNET process is running for SQLNET V1? How about V2? Level: LowExpected answer: For SQLNET V1 check for the existence of the orasrv process. You can use thecommand "tcpctl status" to get a full status of the V1 TCPIP server, other protocols have similar commandormats. For SQLNET V2 check for the presence of the LISTENER process(s) or you can issue the

command "lsnrctl status".





5. What file will give you Oracle instance status information? Where is it located? Level: Low Expectedanswer: The alert.ora log. It is located in the directory specified by the background_dump_dest parameterhe v$parameter table.

6. Users aren?t being allowed on the system. The following message is received: Level: Intermediate OR

00257 archiver is stuck. Connect internal only, until freed What is the problem? Expected answer: Thearchive destination is probably full, backup the archive logs and remove them and the archiver will re-star

7. Where would you look to find out if a redo log was corrupted assuming you are using Oracle mirrorededo logs? Level: Intermediate Expected answer: There is no message that comes to the SQLDBA or

SRVMGR programs during startup in this situation, you must check the alert.log file for this information.

8. You attempt to add a datafile and get: Level: Intermediate ORA-01118: cannot add anymore datafiles:mit of 40 exceeded What is the problem and how can you fix it? Expected answer: When the database w

created the db_files parameter in the initialization file was set to 40. You can shutdown and reset this to ahigher value, up to the value of MAX_DATAFILES as specified at database creation. If the

MAX_DATAFILES is set to low, you will have to rebuild the control file to increase it before proceeding.

9. You look at your fragmentation report and see that smon hasn?t coalesced any of you tablespaces, evehough you know several have large chunks of contiguous free extents. What is the problem? Level: High

Expected answer: Check the dba_tablespaces view for the value of pct_increase for the tablespaces. If pct_increase is zero, smon will not coalesce their free space.

0. Your users get the following error: Level: Intermediate ORA-00055 maximum number of DML locksexceeded What is the problem and how do you fix it? Expected answer: The number of DML Locks is set he initialization parameter DML_LOCKS. If this value is set to low (which it is by default) you will get this

error. Increase the value of DML_LOCKS. If you are sure that this is just a temporary problem, you can ha

hem wait and then try again later and the error should clear.

1. You get a call from you backup DBA while you are on vacation. He has corrupted all of the control filewhile playing with the ALTER DATABASE BACKUP CONTROLFILE command. What do you do?

Level: High Expected answer: As long as all datafiles are safe and he was successful with the BACKUPcontrolfile command you can do the following: CONNECT INTERNAL STARTUP MOUNT (Take any readonly tablespaces offline before next step ALTER DATABASE DATAFILE .... OFFLINE;) RECOVERDATABASE USING BACKUP CONTROLFILE ALTER DATABASE OPEN RESETLOGS; (bring read-onlyablespaces back online) Shutdown and backup the system, then restart If they have a recent output filerom the ALTER DATABASE BACKUP CONTROL FILE TO TRACE; command, they can use that to reco

as well. If no backup of the control file is available then the following will be required: CONNECT INTERNSTARTUP NOMOUNT CREATE CONTROL FILE .....; However, they will need to know all of the datafilesogfiles, and settings for MAXLOGFILES, MAXLOGMEMBERS, MAXLOGHISTORY, MAXDATAFILES fohe database to use the command.



This is the second part of the two part series on helping you answer those tough questions that you might experienceyour quest for an Oracle DBA position.

The Oracle Technical Interview can be quite daunting. You never quite know what to study for and how to prepare. am fully aware of this, as I have received many emails since my original article on interview questions was released

While these questions are only guidelines as to what should and more than likely will be asked, I hope that you findome comfort in the review of them. As always, do not just memorize the answers, as there are jewels to be found inhe quest of figuring out the answer from the question. As always, remember that as you go through the article, it is nough to know the answer to a particular question; you must try to put yourself in an interview situation andxperience answering the question for yourself. Therefore, after you have gone through the questions and answers rhe question again and then answer it with your own words. As always, good luck, and cheers.

Technical - Oracle

Last time, we answered questions 1 thru 20 of the technical part of the interview. Here are the next 30 in this sectionDepending on the mood of the interview and your ability to elaborate on the answer, try to give some insight that yo

know more than just the simple answer to some of these questions. Also, be sensitive to the interviewer getting tiredyou talking too much. Well here they are.

21. How would you determine the time zone under which a database was operating?

elect DBTIMEZONE from dual;

Related Articles

• Oracle Technical Interview Questions Answered - Part1• Oracle Technical Interview

22. Explain the use of setting GLOBAL_NAMES equal to TRUE.

Setting GLOBAL_NAMES dictates how you might connect to a database. This variable is either TRUE or FALSEf it is set to TRUE it enforces database links to have the same name as the remote database to which they are linkin

23. What command would you use to encrypt a PL/SQL application?

WRAP

24. Explain the difference between a FUNCTION, PROCEDURE and PACKAGE.

A function and procedure are the same in that they are intended to be a collection of PL/SQL code that carries a singask. While a procedure does not have to return any values to the calling application, a function will return a single

value. A package on the other hand is a collection of functions and procedures that are grouped together based on thommonality to a business function or application.

http://www.databasejournal.com/features/oracle/article.php/3112661/Oracle-Technical-Interview-Questions-Answered---Part1.htm

http://www.databasejournal.com/features/oracle/article.php/3085171/Oracle-Technical-Interview.htm

http://www.databasejournal.com/features/oracle/article.php/3112661/Oracle-Technical-Interview-Questions-Answered---Part1.htm

http://www.databasejournal.com/features/oracle/article.php/3085171/Oracle-Technical-Interview.htm



Coalescing is only valid for dictionary-managed tablespaces and de-fragments space by combining neighboring freextents into large single extents.

36. What is the difference between a TEMPORARY tablespace and a PERMANENT tablespace?

A temporary tablespace is used for temporary objects such as sort structures while permanent tablespaces are used ttore those objects meant to be used as the true objects of the database.

37. Name a tablespace automatically created when you create a database.

The SYSTEM tablespace.

38. When creating a user, what permissions must you grant to allow them to connect to the database?

Grant the CONNECT to the user.

39. How do you add a data file to a tablespace?

ALTER TABLESPACE <tablespace_name> ADD DATAFILE <datafile_name> SIZE <size>

40. How do you resize a data file?

ALTER DATABASE DATAFILE <datafile_name> RESIZE <new_size>;

41. What view would you use to look at the size of a data file?

DBA_DATA_FILES

42. What view would you use to determine free space in a tablespace?

DBA_FREE_SPACE

43. How would you determine who has added a row to a table?

Turn on fine grain auditing for the table.

44. How can you rebuild an index?



ALTER INDEX <index_name> REBUILD;

45. Explain what partitioning is and what its benefit is.

Partitioning is a method of taking large tables and indexes and splitting them into smaller, more manageable pieces.

46. You have just compiled a PL/SQL package but got errors, how would you view the errors?

HOW ERRORS

47. How can you gather statistics on a table?

The ANALYZE command.

48. How can you enable a trace for a session?

Use the DBMS_SESSION.SET_SQL_TRACE or

Use ALTER SESSION SET SQL_TRACE = TRUE;

49. What is the difference between the SQL*Loader and IMPORT utilities?

These two Oracle utilities are used for loading data into the database. The difference is that the import utility relies ohe data being produced by another Oracle utility EXPORT while the SQL*Loader utility allows data to be loaded t

has been produced by other utilities from different data sources just so long as it conforms to ASCII formatted or delimited files.

50. Name two files used for network connection to a database.

TNSNAMES.ORA and SQLNET.ORA

Technical - UNIX

Every DBA should know something about the operating system that the database will be running on. The questionshere are related to UNIX but you should equally be able to answer questions related to common Windows

nvironments.

. How do you list the files in an UNIX directory while also showing hidden files?

s -ltra



2. How do you execute a UNIX command in the background?

Use the "&"

3. What UNIX command will control the default file permissions when files are created?

Umask

4. Explain the read, write, and execute permissions on a UNIX directory.

Read allows you to see and list the directory contents.

Write allows you to create, edit and delete files and subdirectories in the directory.

Execute gives you the previous read/write permissions plus allows you to change into the directory and executeprograms or shells from the directory.

5. the difference between a soft link and a hard link?

A symbolic (soft) linked file and the targeted file can be located on the same or different file system while for a hardink they must be located on the same file system.

6. Give the command to display space usage on the UNIX file system.

df -lk

7. Explain iostat, vmstat and netstat.

ostat reports on terminal, disk and tape I/O activity.

Vmstat reports on virtual memory statistics for processes, disk, tape and CPU activity.

Netstat reports on the contents of network data structures.

8. How would you change all occurrences of a value using VI?

Use :%s/<old>/<new>/g

9. Give two UNIX kernel parameters that effect an Oracle install

SHMMAX & SHMMNI

0. Briefly, how do you install Oracle software on UNIX.



Basically, set up disks, kernel parameters, and run orainst.

hope that these interview questions were not too hard. Remember these are "core" DBA questions and not necessaelated to the Oracle options that you may encounter in some interviews. Take a close look at the requirements for aob and try to extract questions that interviewers may ask from manuals and real life experiences. For instance, if the

are looking for a DBA to run their databases in RAC environments, you should try to determine what hardware andoftware they are using BEFORE you get to the interview. This would allow you to brush up on particular nvironments and not be caught off-guard. Good luck!

A bitmap index is a type of index that uses a string of bits to quickly locate rows in a table. Bitmapndexes are normally used to index low cardinality columns in a warehouse environment.

edit] History

Bitmap indexes was introduced in Oracle version 7.3.4.

edit] Examples

Bitmap Index:

CREATE BITMAP INDEX emp_bitmap_idx ON big_emp(sex);

Bitmap Join Index:

CREATE BITMAP INDEX emp_dept_loc ON emp(dept.loc)

FROM emp, dept

WHERE emp.deptno = dept.deptno

TABLESPACE index_ts1;

http://www.orafaq.com/wiki/Index

http://www.orafaq.com/wiki/Bit

http://www.orafaq.com/wiki/Row

http://www.orafaq.com/wiki/Table

http://www.orafaq.com/wiki/Cardinality

http://www.orafaq.com/wiki/Column

http://www.orafaq.com/wiki/index.php?title=Bitmap_index&action=edit&section=1

http://www.orafaq.com/wiki/Oracle_7


http://www.orafaq.com/wiki/Index

http://www.orafaq.com/wiki/Bit

http://www.orafaq.com/wiki/Row

http://www.orafaq.com/wiki/Table

http://www.orafaq.com/wiki/Cardinality

http://www.orafaq.com/wiki/Column


http://www.orafaq.com/wiki/Oracle_7


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