ASH Report - How different than AWR report
How to generate ASH Report?
How to read and interpret ASH report?

AWR:
How to identify bad SQL?
Where to look at AWR report or ASH report?

AWR:
--- Gives you only TOP SQLs
--- Other SQLs are executed at the same time which will not be captured in AWR

Example:
--- 1 standard program used to run in 10 second which taking 1 mins.

--- As per Application or business perspective SLA is 10 sec, At any cost this standard SQL has to complete in 10 sec

--- Since this executed within 1 min so it never appeared in AWR report.

Example is Banking transactions

If application team is coming up and complaining out these type of issues and if you want to have a look on these SQLs and issue best way to look at them is ASH report (Active Sessions History)

Application team are coming and complaining at 5:00 PM that morning 10 AM my query was not running properly.

Option1 - You can not check V$SESSION
Option2 - Next option is you may generate AWR and check for the query but no guarantee you may get that SQL
Option3 – ASH comes into picture

select * from v$sgastat where name like 'ASH buffers';
select min(sample_time), max(sample_time) from v$active_session_history;

How to generate the ASH report?
To generate an ASH report on the local database instance using the command-line interface:
@$ORACLE_HOME/rdbms/admin/ashrpt.sql

To generate an ASH report on a specific database instance using the command-line interface:
@$ORACLE_HOME/rdbms/admin/ashrpti.sql

Generating an ASH Report for Oracle RAC
@$ORACLE_HOME/rdbms/admin/ashrpti.sql

https://docs.oracle.com/database/121/TGDBA/sampling.htm#TGDBA279

#ASH #ASHReport #V$SESSIONS #V$ACTIVE_SESSION_HISTORY #DBA_HIST_ACTIVE_SESSION_HISTORY #AWR #Oracle #RAC #Database #Exadata #ASM

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