Re: Rollback Segment Fragmentation

>> Please point me to a manual that covers this or explain how to
determine rollback segment fragmentation. <<

The Concepts manual and Database Administrator's Guide explain everything pretty well. If you use the optimize parameter on your rollback segments the segments are probably not in unnecessary extents. Dropping and recreateing the rollback segments is more likely done to eliminate tablespace fragmentation. If the rollback segments does have unnecessary extents then with Oracle ver. 7.3+ the command 'alter rollback segment seg_name skrink;' can be used to force the segment to give up the extra extents. Normally Oracle only optimizes a rollback segment when looking for another extent within the segment and it determines that the segment is larger than the optimal size and unused extents exist. So a segment will hang onto extents created to support a large job until some other job/transaction fills an extent within the segment and tries to get another one. Kevin Loney's Oracle DBA Handbook gives a good, detailed explanation of rollback segment interanal handling.

Look at the v$rollstat and sys.dba_rollback_segs tables for current information on your segments.

Mark Powell -- The only advise that counts is the advise that you follow so follow your own advise Received on Fri Aug 15 1997 - 00:00:00 CDT