Bill,
A rollback will generate redo, so that it can be recovered. If a
system crashed during a rollback, the database must be able to recover to
the point at which the rollback had terminated. Since a rollback is applying
the undo records (think opposite actions), it is modifying data, so the
modification must be written.
As to why the logs are different sizes, do you by chance have it set
to perform log switchs at regular intervals? What else is in the redo logs?
Are there other records, perhaps related to space management?
Dan Fink
-----Original Message-----
Sent: Thursday, January 16, 2003 2:05 PM
To: Multiple recipients of list ORACLE-L
I recently had a situation where a process went down and Oracle had to
roll back the transaction. The original transaction did around 60,000
inserts and/or updates. When Oracle did its rollback, it generated many redo
logs in a short period of time, but there seems to be a wide variety of
volume per redo log. I used Logminer to check what was written to these logs
during the rollback. Some of them had 1500 - 2000 records written to them
and others had as few as 1 or 2 records written. These, for the most part,
were the same types of records (for example, delete records to roll back the
effects of an insert). Why the disparity? It seems like in many cases, a lot
of redo log is wasted. The reason I am asking is that so many logs were
generated, it filled up my archive log directory before my script could run
to clean them out. Anybody have an explanation?
Bill Carle
AT&T
Database Administrator
816-995-3922
[EMAIL PROTECTED]
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