Want to decrease size for ROLLBACK Segments

Question

my database is oracle8i. Previous DBA increased rollback size to 18GB. i need space on my unix box.
i want to reduce size of rollback segment and utilized this space for other purpose.
This is my stats
Tablespace Name FILE_NAME SIZE IN MB
ROLLBACK /u01/rbsdata/rbs01.dbf 5000
ROLLBACK /u01/rbsdata/rbs02.dbf 5000
ROLLBACK /u01/rbsdata/rbs03.dbf 6000
There are 12 rollback segments allocated to him
SEGMENT_NAME FILE_NAME SIZE
rbs0 /u01/rbsdata/rbs01.dbf 5000
rbs12 /u01/rbsdata/rbs01.dbf 5000
Now Could any one suggest to reduxe size with best performing and not affected my production database.
Thanks
Chetan

Answer 1

Hi Chetan,
You can adapt the following script as per your needs. It will search for all rollback segments other than 'SYSTEM' and construct the sql order to reduce the size of each rollback segment.
connect user/*******@test
SET SERVEROUTPUT ON size 50000
SET HEAD OFF FEEDBACK OFF VERIFY OFF
SPOOL D:\shrink.sql
BEGIN
     -- RBS to be shrinked
     FOR toto IN (select Segment_Name from DBA_SEGMENTS
where Segment_Type = 'ROLLBACK'
and segment_name not in 'SYSTEM')
     LOOP
          DBMS_OUTPUT.PUT_LINE('alter rollback segment '||toto.Segment_Name||' '||'shrink to 60M;');
     END LOOP;
END;
SPOOL OFF
SET HEAD ON FEEDBACK ON VERIFY ON
spool d:\shrink.log
select to_char(sysdate, 'dd/mm/yyyy hh24:mi:ss') "Shrinked" from dual;
@D:\shrink.sql
spool off
Exit
R.Tirou