Re: rbs' maxextents in LMT

[Guang Mei]

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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