Re: calculating segment size issue

John

I believe that you will find that the actual Initial size is 15 blocks or 30K and not 13 blocks or 26K as you believe. If you look at the DBA_EXTENTS where SEGMENT_NAME = 'RB1' I believe you will find that the extent size is 30K. Also, you will find 24 rows being returned (24 extents).

Oracle rounds the segment size upto the nearest 5 block segment size. Something that is mentioned within the Oracle manual set, but can't remember where. Also, if you look under the Extents column, you will see the 24 which is cross verified by the DBA_EXTENTS query.

Rgds
Andrew

john kelly wrote:

> I have a question. I created a rollback segment (called RB1) with the
> following attributes:
>
> SQL>
> SQL> CREATE ROLLBACK SEGMENT RB1 - RB16
> 2 TABLESPACE ROLLBACK_DATA STORAGE (
> 3 INITIAL 25 K
> 4 NEXT 25 K
> 5 MINEXTENTS 24
> 6 ) ;
>
> Rollback segment created.
>
> But when I check it's size in the DBA_segment table I get an initial
> extent of 26624. I was told that it's size is based upon the block
> size (which is 2048). So if I multiply 25k (initial extent) by block
> size I get 12.5. If I round this up to 13 and multiply it by 25k I
> get 26624, Great. But I cant seem to do the same for the bytes size
> of 737280. Can anyone please explain to me what I am doing wrong.
>
> thanks
> John
>
> SQL> select * from dba_segments where segment_type = 'ROLLBACK';
>
> OWNER SEGMENT_NAME
> SEGMENT_TYPE
> ------------------------------
> ---------------------------------------------------------------------------------
> --------------
> TABLESPACE_NAME HEADER_FILE HEADER_BLOCK BYTES
> BLOCKS EXTENTS INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS
> ------------------------------ ----------- ------------ ---------
> --------- --------- -------------- ----------- -----------
> MAX_EXTENTS PCT_INCREASE FREELISTS FREELIST_GROUPS
> ----------- ------------ --------- ---------------
> SYS RB1
> ROLLBACK
> ROLLBACK_DATA 6 2 737280
> 360 24 26624 26624 24
> 121 0 1 1
Received on Mon Apr 19 1999 - 20:00:27 CDT