Re: Minextents for rbsseg in LMT tablespace

In article <3bf0f837$0$214$edfadb0f_at_dspool01.news.tele.dk>, "Peter says...
>
>Hi,
>
>System: 8.1.6
>I have a ora-1555 problem that i can solve by upping the minextents
>parameter for my rollback segments in a dictionary managed tablespace.
>However at some customers I have made the rbs tablespace LMT with uniform
>size. It seemed like a good idea, but for a LMT you cant specify minextents
>or rather you can have a storage clause when creating a rollback segment but
>the clause but is is ignored.
>
>What to do?
>Id rather not go back to dict managed rbs but do I have other choices?
>
>TIA
>Peter Laursen
>
>
>
>
>

  1 select initial_extent, next_extent, extent_management   2* from dba_tablespaces where tablespace_name = 'USERS' ops$tkyte_at_ORA817DEV.US.ORACLE.COM> /

INITIAL_EXTENT NEXT_EXTENT EXTENT_MAN
-------------- ----------- ----------

        524288 524288 LOCAL ops$tkyte_at_ORA817DEV.US.ORACLE.COM> create rollback segment foobar   2 storage ( minextents 25 ) tablespace users;

Rollback segment created.

ops$tkyte_at_ORA817DEV.US.ORACLE.COM> select segment_type, extent_id, blocks   2 from dba_extents where segment_name =   3 'FOOBAR'; SEGMENT_TYPE EXTENT_ID BLOCKS

------------------ ---------- ----------
ROLLBACK                    0         64
ROLLBACK                    1         64
ROLLBACK                    2         64
ROLLBACK                    3         64
ROLLBACK                    4         64
ROLLBACK                    5         64
ROLLBACK                    6         64
ROLLBACK                    7         64
ROLLBACK                    8         64
ROLLBACK                    9         64
ROLLBACK                   10         64
ROLLBACK                   11         64
ROLLBACK                   12         64
ROLLBACK                   13         64
ROLLBACK                   14         64
ROLLBACK                   15         64
ROLLBACK                   16         64
ROLLBACK                   17         64
ROLLBACK                   18         64
ROLLBACK                   19         64
ROLLBACK                   20         64
ROLLBACK                   21         64
ROLLBACK                   22         64
ROLLBACK                   23         64
ROLLBACK                   24         64

25 rows selected.

Minextents works just fine on LMTs....

When you use a storage clause on an LMT, it is not accurate to say its "ignored" perhaps - rather then it is used to conform to the rules

what happens is the INITIAL, NEXT, MINEXTENTS -- etc are used to compute how big the object would have allocated in a DMT -- then we divide by the size of the extents in the LMT, round up and there we go -- thats how many extents we'll allocate.

For example:

ops$tkyte_at_ORA817DEV.US.ORACLE.COM> drop rollback segment foobar; Rollback segment dropped.

ops$tkyte_at_ORA817DEV.US.ORACLE.COM> create rollback segment foobar   2 storage ( initial 12800k ) tablespace users; Rollback segment created.

ops$tkyte_at_ORA817DEV.US.ORACLE.COM> select count(*) from dba_extents where segment_name = 'FOOBAR';

  COUNT(*)

        26

Using a big initial -- we got what we asked for -- just in separate extents. Again:

ops$tkyte_at_ORA817DEV.US.ORACLE.COM> drop rollback segment foobar;

Rollback segment dropped.

ops$tkyte_at_ORA817DEV.US.ORACLE.COM> create rollback segment foobar   2 storage ( initial 1m next 1m minextents 5 ) tablespace users;

Rollback segment created.

ops$tkyte_at_ORA817DEV.US.ORACLE.COM> select count(*) from dba_extents where segment_name = 'FOOBAR';

  COUNT(*)

        10

we got what we asked for -- 5meg of rollback -- it just took 10 extents in this LMT to do it.

--
Thomas Kyte (tkyte@us.oracle.com)             http://asktom.oracle.com/ 
Expert one on one Oracle, programming techniques and solutions for Oracle.
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