Oracle-L: Re: rbs' maxextents in LMT

From: Guang Mei <zlmei_at_hotmail.com>
Date: Tue, 07 Jan 2003 11:08:45 -0800
Message-ID: <F001.00528EA9.20030107110845@fatcity.com>

Hi, Arup:

I created lmt "rbs" this way:

CREATE TABLESPACE RBS
DATAFILE '/oracle/u02/oradata/YPD/rbs01.dbf' SIZE 2048M EXTENT MANAGEMENT LOCAL
UNIFORM SIZE 2M; and then

SQL> create rollback segment RBSTest1 storage(initial 2048K next 2048K) tablespace rbs;

Rollback segment created.

SQL> create rollback segment RBSTest2 storage(initial 2048K next 2048K MAXEXTENTS 300) tablespace rbs;

Rollback segment created.

SQL> select SEGMENT_NAME,INITIAL_EXTENT,NEXT_EXTENT,   2 MIN_EXTENTS,MAX_EXTENTS
  3 from dba_rollback_segs
  4 where SEGMENT_NAME like '%TEST%';

SEGMENT_NAME                   INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS
------------------------------ -------------- ----------- -----------

MAX_EXTENTS

RBSTEST1                              4194304     2097152           1
      32765

RBSTEST2                              4194304     2097152           1
      32765

It shows that you can not set MAXEXTENTS of a rollback segment when it is created in LMT. What I mean the "run away transaction" is a transaction that keep using rollback segment until it uses up all it's extents. In DMT case, we can set the MAXEXTENTS of all the rollback segments so that there is no transaction that can use the whole tablespace. But in LMT, it seems a "run away" transaction can "eat up" the whole rbs tablespace because there is no MAXEXTENTS ( ie, MAXEXTENTS = unlimited). Does anyone know there is somewhere in Oracle Doc that I can find the answer of my question?

Thanks.

Guang

Date: Mon, 06 Jan 2003 18:10:08 -0500

Guang,

You should use LMTs with UNFORM extent allocation of some size So create the tablespaces and the rollback segments but not the INITIAL or NEXT.

I am not sure what you meamn by runaway processes. If a transaction needs rollback segment space, it will need to extend it. You can still specify MAXEXTENTS to limit the number of extents.

HTH Arup

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Author: Guang Mei
INET: zlmei_at_hotmail.com

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