awr

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AWR[AUTOMATED WORKLOAD REPOSITORY][AUTOMATED WORKLOAD REPOSITORY]

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1. Birth of Awr.

2. What is Awr.

3. Features In Awr.

4. Installation of Awr.

5. Running Awr.1. Creating a Report.

2. Modifying the Default Setting.

3. Creating Extra Snapshot.

4. Dropping a Snapshot.

5. Creating a Baseline Snapshot.

6. Dropping a Baseline Snapshot.

7. Comparing the Two Reports.

6. Awr VS Stats pack.

7. View & Tables in Awr.

8. Awr in Enterprise Manager

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AWR Birth

• Historically people used bstat and estat to collect Oracle statistics over a time period and then compare them to each other.

• The bstat / estat approach was replaced with Statspack available in Oracle 8i. Statspack was a package provided by Oracle that did roughly the same thing but better.

• Statspack has now been surpassed in functionality by AWR which is always collecting execution statistics for future analysis and tuning performed by all of the expert components provided by Oracle. Oracle recommends that all statspack users switch to AWR in 10g.

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WHAT IS AWR?

• The main focus of the Oracle Database 10g is self-manageability.

• Automated Workload Repository is the place where the data to aid in self management are stored.

• AWR is a new feature in 10g which is used for monitoring , analyzing the performance of the database and solutions recommendation for tuning process for DBA's.

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Metrics Collected By AWR

Metrics Collected By the AWR Can be obtained by view v$metricname

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AWR FEATURES

The AWR is used to collect performance statistics including:

• Wait events used to identify performance problems

• Time model statistics indicating the amount of DB time associated with a process from the V$SESS_TIME_MODEL and V$SYS_TIME_MODEL views.

• Active Session History (ASH) statistics from the V$ACTIVE_SESSION_HISTORY view.

• Some system and session statistics from the V$SYSSTAT and V$SESSTAT views.

• Object usage statistics.

• Resource intensive SQL statements.

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AWR is automatically installed and running with 10g. The new MMON process is responsible for collecting data and

populating the AWR. We can confirm it by the Linux command.

INSTALLATION OF AWR

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RUNNING AWR

1.How to Generate a report.

2.Modifying the Default Settings.

3.Creating an extra snapshots.

4.Droping a snapshot.

5.Creating a Baseline Snapshot.

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RUNNING A REPORT

To Run AWR there are two preloaded scripts 10g at the location

• @$ORACLE_HOME/rdbms/admin/awrrpt.sql

• @$ORACLE_HOME/rdbms/admin/awrrpti.sql

• These both scripts are similar to the statspack reports gives the option of HTML or plain text formats to save the output. Both scripts gives the same output where us awrrpti.sql lets us to select a single instance.

• When we execute these scripts it prompts us to enter the format of the report [HTML or TEXT],

• Start snapshot id, End snapshot id and Report filename. The result can be viewed in a browser or text editor accordingly.

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Specifying the Report Type

Specifying the Dbid & Instance Number

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Specifying the Number of Days Snapshots to Choose from

Choosing the Begin and End Snap Value

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Specifying the Report Name and Final Result

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ERROR

When an instance is shutdown between two snapshots it will return a error like.

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Modifying The Default Settings

By Default the snapshots are taken every hour and retained for 7 days .These Default Values can be altered by

No of days snapshot will be retained

Snapshots will be taken at a time interval of 10 minutes.

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The changes in the snapshot settings are updated in the table DBA_HIST_WR_CONTROL.

Edited Time Interval

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Creating An Extra Snapshot

• If we need an extra snapshot in between the interval time means we can use the command below.

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Dropping Snapshots

• With the help of the command given below we can drop the snapshots.

• The command will delete the Snapshots From 22 to 32.

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Procedure to Purge the Reports according to user given no of days

set serveroutput on

declare

v_beginsnap number;

v_endsnap number;

cursor test is

select min(snap_id),max(snap_id)from dba_hist_snapshot where startup_time<sysdate-&noofdays order by snap_id;

begin

open test;

for i in 1..1 loop

fetch test into v_beginsnap,v_endsnap;

dbms_output.put_line (v_beginsnap||' '||v_endsnap);

end loop;

close test;

DBMS_WORKLOAD_REPOSITORY.drop_snapshot_range (

low_snap_id => v_beginsnap,

high_snap_id => v_endsnap);

END;

/

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Creating a Baseline Snapshot.

• Baseline is a pair of snapshot that represents a specific period of usage.

• A snapshot will be taken at the normal period when the instance is running smoothly and when the database is doing some large operations. These snapshots will be compared with the snapshot taken at the time of any problem in the database.

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Dropping a Baseline Snapshot

• The pair of snapshots associated with a baseline are retained until the baseline is explicitly deleted

Deletes associated snapshots if TRUE

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• Baseline Information Can be Gathered from the table

DBA_HIST_BASELINE.

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Comparing The Two Reports

Comparing Baseline Report and Newly Generated Report

• AWR Compare Period report provides comparison of two snapshot periods.

• To compare the two reports there is a preloaded script in oracle 10g. @$ORACLE_HOME/rdbms/admin/awrddrpt.sql.

• Results are ordered by statistical differences between the two periods.

• Comparison can also be done through EM.

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STEPS TO COMPARE

1.Run the report @$ORACLE_HOME/rdbms/admin/awrddrpt.sql.

2. Specify the report type by default it is HTML.

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3. Specify the No of Days for the first pair of snapshots.

4. Specify the first pair of snapshots Begin & End Snapid’s.

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5. Specify the No of Days for the second pair of snapshots.

6. Specify the second pair of snapshots Begin & End Snapid’s.

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7. Specify the report name

NOTE-While entering the no of days we should be careful because entering the no of days will list the most recent snapshots. So to list the baseline snapshot ids the no of days should be sysdate - start_snap_time. The start_snap_time can be querried from dba_hist_sanspshot table.

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COMPARED REPORT and a NORMAL REPORT

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AWR [vs] STATSPACK• Statspack does not store history for new metric statistics

introduced in Oracle10g. The key AWR views, dba_hist_sysmetric_history and

dba_hist_sysmetric_summary. dba_hist_service_stat , dba_hist_service_wait_class and dba_hist_service_name , which store history for performance cumulative statistics tracked for specific services.

• Statspack snapshots must be run by an external scheduler like (dbms_jobs, CRON, etc.).

AWR snapshots are scheduled every 60 minutes by default.We can change the interval by adjusting the snapshot interval if we desired to.The new background process MMON is reponsible for initiating the snapshot automatically.

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• When the Statspack tablespace runs out of space, Statspack quits working. The snapshot collected by the Statspack should be purged manually.

In AWR snapshots are purged automatically by MMON every night. MMON, by default, tries to keep one week's worth of AWR snapshots available. If AWR detects that the SYSAUX tablespace is in danger of running out of space, it will free space in SYSAUX by automatically deleting the oldest set of snapshots. If this occurs, AWR will initiate a server-generated alert to notify administrators of the out-of-space error condition.

Administrators can manually adjust the amount of information retained by invoking the MODIFY_SNAPSHOT_SETTINGS PL/SQL stored procedure and specifying the RETENTION parameter input variable.

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AWR VIEWS AND TABLES

• V$ACTIVE_SESSION_HISTORY - Displays the active session history (ASH) sampled every second.

• V$METRIC - Displays metric information.• V$METRICNAME - Displays the metrics associated with each

metric group.• V$METRIC_HISTORY - Displays historical metrics.• V$METRICGROUP - Displays all metrics groups.• DBA_HIST_ACTIVE_SESS_HISTORY - Displays the history

contents of the active session history.• DBA_HIST_BASELINE - Displays baseline information.• DBA_HIST_DATABASE_INSTANCE - Displays database

environment information.• DBA_HIST_SNAPSHOT - Displays snapshot information.• DBA_HIST_SQL_PLAN - Displays SQL execution plans.• DBA_HIST_WR_CONTROL - Displays AWR settings.

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AWR IN ENTERPRISE MANAGER

• The automated workload repository administration tasks have been included in Enterprise Manager.

• The "Automatic Workload Repository" page is accessed from the main page by clicking on the "Administration" link, then the "Workload Repository" link under the "Workload" section.

• The page allows you to modify AWR settings or manage snapshots without using the PL/SQL APIs.

THANK YOUSANJAY BALA.ADOYENSYS

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AWR Frequently Asked Questions

1. What Is AWR.

2. How to confirm the Awr running.

3. How to modify the default settings.

4. How to create a extra snapshot in between the interval.

5. How to generate a Baseline report.

6. How to automatically purge the sysaux tablespace.

7. How to compare the Baseline report with the last taken report.