Re: Rollback segments and optimal size
Date: Fri, 25 Mar 1994 13:21:28 GMT
Message-ID: <Cn82Ft.5FL_at_freenet.carleton.ca>
In a previous article, gerrit_at_vtm.be (The Administrator) says:
>At what point in time does a rollback segment gets shrinked to it's optimal
>size ? Can it be forced to do so ?
The shrink occurs when the extent currently being written to fills. Before moving on to the next extent, Oracle checks to see if the current segment size is greater than the optimal size, if so it discards one extent, and then repeats until the optimal size is reached.
If you are in a hurry to shrink a rollback segment, say RBS_1:
ROLLBACK;
SET TRANSACTION USE ROLLBACK SEGMENT RBS_1;
DELETE SYSTEM.HELP WHERE ROWNUM <= 1000;
ROLLBACK;
The delete statement can be any DML statement which will produce
enough undo entries to fill the current extent. Depending on your
extent sizes, you may need to do this a few times before v$rollstat
shows the shrink has occurred.
- Doug Harris Database Administrator, System Development Division, Statistics Canada ## Standard Disclaimer Applies ## --