but the rollback segment could be shrunk to optimal in the course of
Oracle going about its business in the database (say another user is
assigned to that rollback segment and needs to extend, Oracle will
first shrink it before extending).
and if no one is accessing the data in the rollback segment that is
being shrunk then it won't cause an ora-1555 at all.
so you can't really say that a shrink will cause an ora-1555. There's
more to the cause of the ora-1555 than just shrinking the rollback
segment
- "Johnston, Tim" <TJohnston_at_quallaby.com> wrote:
> Can what cause a ORA-1555? A shrink? If that is the question...
> The
> answer is yes...
>
> Tim
>
> -----Original Message-----
> Sent: Thursday, January 31, 2002 11:00 PM
> To: Multiple recipients of list ORACLE-L
>
>
> Will this cause ora 1555 ?
>
> -----Original Message-----
> Tim
> Sent: 31 January 2002 03:31
> To: Multiple recipients of list ORACLE-L
>
>
> Um... Must be version differences... Here is a test case I ran on
> my
> 8.1.7.3 machine...
>
> SQL> create public rollback segment tim tablespace rbs storage (
> initial 1M
> next 1M minextents 20 maxextents 100 optimal 20M );
>
> Rollback segment created.
>
> SQL> alter rollback segment tim online;
>
> Rollback segment altered.
>
> SQL> select segment_name, min_extents, initial_extent, next_extent
> 2 from dba_segments
> 3 where segment_name = 'TIM';
>
> SEGMENT_NAME MIN_EXTENTS INITIAL_EXTENT NEXT_EXTENT
> ------------------------------ ----------- -------------- -----------
> TIM 20 1048576 1048576
>
> SQL> select rs.extents, rs.rssize/1048576 , rs.optsize/1048576
> 2 from dba_rollback_segs drs,
> 3 v$rollstat rs
> 4 where drs.segment_name = 'TIM'
> 5 and drs.segment_id = rs.usn;
>
> EXTENTS RS.RSSIZE/1048576 RS.OPTSIZE/1048576
> ---------- ----------------- ------------------
> 20 20.296875 20
>
> SQL> alter rollback segment TIM shrink to 10M;
>
> Rollback segment altered.
>
> SQL> select segment_name, min_extents, initial_extent, next_extent
> 2 from dba_segments
> 3 where segment_name = 'TIM';
>
> SEGMENT_NAME MIN_EXTENTS INITIAL_EXTENT NEXT_EXTENT
> ------------------------------ ----------- -------------- -----------
> TIM 20 1048576 1048576
>
> SQL> select rs.extents, rs.rssize, rs.optsize
> 2 from dba_rollback_segs drs,
> 3 v$rollstat rs
> 4 where drs.segment_name = 'TIM'
> 5 and drs.segment_id = rs.usn;
>
> EXTENTS RSSIZE OPTSIZE
> ---------- ---------- ----------
> 10 10633216 20971520
>
> SQL> alter rollback segment tim offline;
>
> Rollback segment altered.
>
> SQL> drop rollback segment tim;
>
> Rollback segment dropped.
>
> SQL>
>
> What version is your test running on?
>
> Tim
>
> PS - Here is my test case if you want to run it...
>
> column segment_name format a30
> create public rollback segment tim tablespace rbs storage ( initial
> 1M next
> 1M minextents 20 maxextents 100 optimal 20M );
> alter rollback segment tim online;
> select segment_name, min_extents, initial_extent, next_extent
> from dba_segments
> where segment_name = 'TIM';
> select rs.extents, rs.rssize/1048576 , rs.optsize/1048576
> from dba_rollback_segs drs,
> v$rollstat rs
> where drs.segment_name = 'TIM'
> and drs.segment_id = rs.usn;
> alter rollback segment TIM shrink to 10M;
> select segment_name, min_extents, initial_extent, next_extent
> from dba_segments
> where segment_name = 'TIM';
> select rs.extents, rs.rssize, rs.optsize
> from dba_rollback_segs drs,
> v$rollstat rs
> where drs.segment_name = 'TIM'
> and drs.segment_id = rs.usn;
> alter rollback segment tim offline;
> drop rollback segment tim;
>
> -----Original Message-----
> Sent: Wednesday, January 30, 2002 2:17 PM
> To: Multiple recipients of list ORACLE-L
>
>
> testing....
>
> if the initial extent*min_extents is less than the optimal, yes you
> can
> shrink below optimal.
>
> if initial*minextents = optimal, you can execute an alter rollback
> segment statement that lists a shrink size that is less than optimal
> AND less than initial*minextents and it will not fail. But if you
> LOOK
> at the size it shrinks to, it's initial*minextents.
>
> so you can "kinda" shrink below optimal, the statement won't fail,
> but
> Oracle will ignore the number you give it.
>
>
> --- "Johnston, Tim" <TJohnston_at_quallaby.com> wrote:
> > You know what? I thought the same thing... But, the curious side
> of
> > me
> > decided to give it a try to be sure... And guess what... It
> works?
> > Learn
> > something new everyday...
> >
> > SQL> select segment_name,sum(bytes) from dba_segments where
> > tablespace_name
> > = 'RBS' and segment_name
> > = 'RBS17' group by segment_name;
> >
> > SEGMENT_NAME SUM(BYTES)
> > ------------------------ ----------
> > RBS17 22364160
> >
> >
> > SQL> select rs.optsize, rs.extents
> > 2 from dba_rollback_segs drs,
> > 3 v$rollstat rs
> > 4 where drs.segment_name = 'RBS17'
> > 5 and drs.segment_id = rs.usn;
> >
> > OPTSIZE EXTENTS
> > ---------- ----------
> > 22020096 21
> >
> > SQL> alter rollback segment RBS17 shrink to 10M;
> >
> > Rollback segment altered.
> >
> > SQL> select segment_name,sum(bytes) from dba_segments where
> > tablespace_name
> > = 'RBS' and segment_name
> > = 'RBS17' group by segment_name;
> >
> > SEGMENT_NAME SUM(BYTES)
> > ------------------------- ----------
> > RBS17 10649600
> >
> >
> > SQL> select rs.optsize, rs.extents
> > 2 from dba_rollback_segs drs,
> > 3 v$rollstat rs
> > 4 where drs.segment_name = 'RBS17'
> > 5 and drs.segment_id = rs.usn;
> >
> > OPTSIZE EXTENTS
> > ---------- ----------
> > 22020096 10
> >
> > SQL>
> >
> > 8.1.7.3 on Solaris 2.8
> >
> > Tim
> >
> > -----Original Message-----
> > Sent: Wednesday, January 30, 2002 10:26 AM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > no, you can't shrink a rollback segment below the optimal value
>
=== message truncated ===
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