Re: Rollback Segment
Date: 1995/05/12
Message-ID: <3ovqd5$i52_at_linus.mitre.org>#1/1
Phuong Quach (quach_at_ext423.artecon.com) wrote:
: Hi all,
: Thanks in advance for all answers for the below questions:
:
: When do I need to create rollback segment? (using CREATE ROLLBACK..)
: When do I need to add more datafiles to the rollback tablespace (using ALTER TABLESPACE)?
You would only need to add a datafile if when users running large updates
receive the stating that oracle failed to allocate extent of size #### in
tablespace {rollback tablespace name}. This could be either because your
extent sizes do not fit evenly in the tablespace or you truely have run
out of space. You can query v$rollstat to see how you rollback segments
are doing.
: In what circumstances the rollback segment can slow down the performance?
Doing the query above can help in tracking performance. Basically for
large update and such, the rollback segment and extent size should be large.
An example I had a customer who was doing massive update to a 120GB table
and the process was taking 3 hours. Their initial and next extent size
on their large rollback segment was 1MB or less. I changed it to 10MB and
all of their process were 45% faster. That above process started finishing
in 50 minutes. Figure that the more times the rollback segment has to
extent itself the slower the process.
: quach_at_artecon.com
Received on Fri May 12 1995 - 00:00:00 CEST