Oracle-L: Re: rollback segment

From: Darrell Landrum <DLANDRUM_at_zalecorp.com>
Date: Fri, 14 Mar 2003 14:44:19 -0800
Message-ID: <F001.0056AE21.20030314144419@fatcity.com>

ak,

Here is a query you can run to see if it is currently in use...

SQL> select b.segment_name, a.xacts, a.shrinks, a.wraps, a.extends 2 from v$rollstat a, dba_rollback_segs b 3 where a.usn = b.segment_id
4 /

SEGMENT_NAME                        XACTS    SHRINKS      WRAPS    EXTENDS
------------------------------ ---------- ---------- ---------- ----------
SYSTEM                                  0          0          0          0
RBS_BIG01                               0          1         46          6
RBS_BIG02                               0          1         57          8
RBS_BIG03                               0          0         31          0
RBS_BIG04                               1          4         86         27
RBS_BIG05                               1          1         43          8

6 rows selected.

What you're looking for here is the 'XACTS' column to be zero for the rollback segment you want to take offline. Once you see it is not in use, shrink it: 'alter rollback segment RBSNAME shrink;'. Then take it offline. If it is taking up too much space, maybe drop and recreated it with smaller extent sizes, but I wouldn't just drop it. This is a good rollback segment to have handy to bring online under special circumstances. Also, you might check any available code to ensure no one is explicitly using this rollback segment in their sql code.

Darrell

>>> oramagic_at_hotmail.com 03/14/03 03:53PM >>>
I have recently found that one temporary rollback segment in system tablespace is having more then 600 extnets . It looks like previous dba created this rollback segment at the time of db creation and forgot to take it offline . Now how do I find it this rollback segment is being used actively . I see values in gets , writes from v$rollstat view .

What step should I take to drop this rollback segment . What implication might have if I take this offline ? I want to relase the space taken by this rollback segment ( >600 extents ..thats big ) , so just taking offline wont do this.

Are there any views accessible from system( no sys) account which can tell me which trasaction is using which rollback segment .

thanks
-ak

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Author: Darrell Landrum
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Received on Fri Mar 14 2003 - 16:44:19 CST