Oracle-L: What gets written to redo on a rollback?

From: Carle, William T (Bill), ALCAS <wcarle_at_att.com>
Date: Thu, 16 Jan 2003 13:04:32 -0800
Message-ID: <F001.0053210D.20030116130432@fatcity.com>

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
wcarle_at_att.com

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Author: Carle, William T (Bill), ALCAS
INET: wcarle_at_att.com

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