Oracle Using the Undo and Redo Logfile Size Advisors

 

Oracle Tips by Burleson Consulting

This is an excerpt from "Oracle 10g New Features for Administrators" by Ahmed Baraka.

Undo Advisor

The Undo Advisor helps you perform the following tasks:

o Set the undo retention period

o Set the size of the undo tablespace

To access the Undo Advisor in the Database Control:

Follow the links: Database Control home page, Administration, Undo Management button, the Undo Advisor button in the right corner.

Redo Logfile Size Advisor

The Redo Logfile Size Advisor will make recommendations about the smallest online redo log files you can use.

The Redo Logfile Size Advisor is enabled only if you set the FAST_START_MTTR_TARGET parameter.

Check the column OPTIMAL_LOGFILE_SIZE in V$INSTANCE_RECOVERY view to obtain the optimal size of the redo log file for your FAST_START_MTTR_TARGET setting.

To access the Redo Logfile Size Advisor:

1. Database Control home page, Administration, Under the Storage section, Redo Log     Groups.

2. Select any redo log group, and then choose the Sizing Advice option from the Action    drop-down list, Click Go

Rollback Monitoring

In Oracle Database 10g, when a transaction rolls back, the event is recorded in the view V$SESSION_LONGOPS, if the process takes more than six seconds. This view enables you to estimate when the monitored rollback process will finish.

SELECT TIME_REMAINING,
SOFAR/TOTALWORK*100 PCT
FROM V$SESSION_LONGOPS
WHERE SID = 9
AND OPNAME ='Transaction Rollback'