I realized that my procedure cases a big undo problem...
As soon as more than one user starts calling my procedure it starts performing extremely slowly. It happens when they call it from another application, but when I call it directly it works OK.
It actually selects and retrieves a lots of data, thousands of records.
Any idea how to solve the problem.
I'm using dynamic sql and I know that commit frees undo space but it would not allow me to use commit. It gives me exception:
SQL Error: ORA-14552: cannot perform a DDL, commit or rollback inside a query or DML
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My procedures work properly, the queries have good explain plane, when accessed directly have no problem but when accessed from another application by more than one user via webmethods it becomes real pain. It causes undue stress :)
I thought I needed to add something else... as many users retrieve thousands and thousands of data
Since you did not provide your SQL or explain exactly what you are doing, I am going to guess that your problem may not have much to do with UNDO. It could be multi-user contention of writing to the same table. Do you have any bitmap indexes perhaps?
Try general tuning approaches as well, such as increasing the SGA.
Also consider materialized views to speed up intermediate result sets / subqueries.
Use enterprise manager to view the SQL Advisor for some suggestions on tuning.
Also consider taking a snapshot of v$sysstat into a temp table t1, then run your queries a few times, then take another snapshot into table t2, then compare the results for differenecs and see if there are disk sorts, full scans, waits, etc. in the values that are different.
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by: grzessioPosted on 2009-07-02 at 22:59:27ID: 24770221
if your procedure only selects and retreives data from table (without modification) then undo is not used unless someone else changes this data.
any code would be helpful.