Muhammad Umair

Services of DBMS

Oracle Database 11g Developer Track

› Database Security› Database Recovery› Data Integrity› Transaction Support› Concurrency Control

Services of DBMS

› Database Security– DBMS furnishes mechanisms to prevent data from accidental or

intentional looses, destruction or misuse.– Two of common security mechanisms are:

› Authentication– DBMS requires people to prove their identity before connecting to

the database› Authorization

– DMBS enable developers to define right or privileges of the database users

Database Security

› Database Recovery– DBMS furnishes mechanisms to restore data efficiently and

accurately after any type of loss od damage– Two of the recovery mechanisms are:

› Back-up– A copy of database is maintained to be use for recovery in case

of damage of the whole or some of its parts› Change-log Maintenance

– The changes mage to the data are recorded so that data may be restored to some of its previous state.

Database Recovery

› Data Integrity– DBMS furnishes mechanisms to ensure that only valid data in

entered into the database› Data integrity mechanisms:

– Enable developers to define constraints on data.– Enable developers to create code segments to ensure validity of

data before or after some DML statements for example triggers

Data Integrity

› Transection Support Service– DBMS furnishes mechanisms to ensure that either all updates

included in a transaction are made or none of them is made.– As part of transection support mechanisms DBMS let user to

commit or rollback their transactions

Transection Support

› Concurrency Control Service– DBMS furnishes mechanisms to prevent from data inconsistency

when two or more transaction occurs same data at same time.› Locking Mechanism

– A resource accessed by a transaction is banned for other transaction until that transaction completed.

– There are two types of locks– Shared Lock

› A lock that is applied for readers. It can be shared by many transaction– Exclusive Lock

› A lock that is applied for writers. It cant be shared by different transaction

Concurrency Control

› Dead Lock– A situation in which locks don’t resolve by automatic process,

until DBMS takes special action for their resolution– In a database, a deadlock is a situation in which two or more

transactions are waiting for one another to give up locks. For example, Transaction A might hold a lock on some rows in the Accounts table and needs to update some rows in the Orders table to finish

Services of DBMS