RE: Rollback Segment Problem

From: Mohammad Rafiq <rafiq9857_at_hotmail.com>
Date: Wed, 13 Feb 2002 11:22:10 -0800
Message-ID: <F001.0040E5E7.20020213111415@fatcity.com>

Thanks...even is not true completely...if you have seen responses of Sameer Sarkar, originator of this thread...resolved his problem after coalesing his rbs table_space...

I have to dealt with this situation on one of our databases because of some codes which results in lot of shrinkage of rollback segment and we have to coalesce that rbs tablespace quit often to get scattered/fragmented extents in contitgous extents....

Regards
Rafiq

Reply-To: ORACLE-L_at_fatcity.com
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: Wed, 13 Feb 2002 10:28:58 -0800

IN THIS CASE yes, but NOT BEFORE.... That was my point. Thanks,
Best,
Sergey

-----Original Message-----

Sent: Wednesday, February 13, 2002 12:54 PM To: Multiple recipients of list ORACLE-L

In many cases you will have to take RB segments offline and drop them, then re-create

------Even in this case you have to coalesce rbs tablespace before
recreating rollback segments using that particular tablespace to make all released extents as contigous...Besides it is a good practice to reorg rollback segments..

Regards
Rafiq

Reply-To: ORACLE-L_at_fatcity.com
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: Wed, 13 Feb 2002 08:58:47 -0800

Hi, guys,
Just my $0.02, coalescing free space will NEVER eliminate fragmentation. In many cases you will have to take RB segments offline and drop them, then re-create. In the interim period you might want to have a big rollback segment(or a few) in another tablespace. Best,
Sergey

-----Original Message-----

Sent: Wednesday, February 13, 2002 11:03 AM To: Multiple recipients of list ORACLE-L

Samir,
It is not coalesced automatically at shutdown and startup. It is to be coalesced manually. It applies to any tablespace with pctincrease set as 0(zero). I have no idea of 9i but this is normal behaviour of ver 7.3.4 to 8.1.7...

Regards
Rafiq

Reply-To: ORACLE-L_at_fatcity.com
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: Wed, 13 Feb 2002 05:48:28 -0800

Rafiq,

Just a small question....r the rollback segment extents in the rollback segment tablespace de-allocated when the database is shut down ?? In that case, does the fragmentation remain when the database is restarted or r the blocks coalesced automatically ??

Regards,
Samir

Samir Sarkar
Oracle DBA - Lennon Team
SchlumbergerSema
Email : samir.sarkar_at_nottingham.sema.slb.com

samir.sarkar_at_sema.co.uk
Phone : +44 (0) 115 - 957 6217
EPABX : +44 (0) 115 - 957 6418 Ext. 76217 Fax : +44 (0) 115 - 957 6018

-----Original Message-----

Sent: 12 February 2002 17:49
To: Multiple recipients of list ORACLE-L

Is your tablespace fragmented as it is not finding contingous extent .. TRy to coalesce your subject tablespace and try...

you can use following script to check whether coalesing is required or not.. If percent is < 100 then coalesce it..

select substr(tablespace_name,1,10)TS_NAME,total_extents "Total_Extnts",extents_coalesced,round(percent_extents_coalesced,0) from dba_free_space_coalesced
order by tablespace_name
/

HTH
Regards
Rafiq

Reply-To: ORACLE-L_at_fatcity.com
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: Tue, 12 Feb 2002 02:33:19 -0800

All,

The following is the pitiable scenario I am in and would really appreciate a bit of help :

We were running a long running delete job which gave the following error
:

                                 Oracle8 Enterprise Edition Release
8.0.5.2.1 - Production
                                PL/SQL Release 8.0.5.2.0 - Production
                                SQLWKS> EXECUTE

PKG_PAS_AnnualDataMaintenance.Delete_OldData (2000, '/home/sqribe/work/live', '2000AnnualDataDelete.log');

                                ORA-01562: failed to extend rollback segment
number 8
                                ORA-01650: unable to extend rollback segment
RSUNDB08 by 50 in tablespace RSUN425
                                ORA-06512: at
"PAS.PKG_PAS_ANNUALDATAMAINTENANCE", line 66
                                ORA-06512: at line 2


     I don't understand why it ran out of rollback space. The rollback

segment
has a virtually unlimited number of extents, so the only explanation I can see is that this particular rollback segment expanded until it exceeded the space allocation for the whole tablespace RSUN425, which is 3,000M. However, Oracle Storage Manager shows only 200M of the tablespace used, and it also shows high water marks against each rollback segment, none of which exceeds 400M. This would suggest to me that none of the previous month's deletions exceeded 400M per month, so why should it fail on this particular one when it had nearly 3,000M available?

Is there something I am not understanding about rollback segments ??

Thanks and Regards,
Samir

Samir Sarkar
Oracle DBA - Lennon Team
SchlumbergerSema
Email : samir.sarkar_at_nottingham.sema.slb.com

                samir.sarkar_at_sema.co.uk

Phone : +44 (0) 115 - 957 6217
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Author: SARKAR, Samir

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