EMEA PeopleSoft Roadshow 2014

Monday, April 06, 2009

Statistics Management for PeopleSoft Temporary Records in Application Engine Programs

Last year, I wrote about Oracle Optimizer Statistics and Optimizer Dynamic Sampling with PeopleSoft Temprorary Records. Earlier this year, I encountered a situation where Optimizer Dynamic Sampling was not sufficient, and I did need properly gathered statistics on an object. I modified my PL/SQL packaged procedure wrapper which can be called by the %UpdateStats PeopleCode macro via a customised DDL model to collects statistics.

I still recommend locking statistics on PeopleSoft Temporary Record, so that table is omitted from schema or database wide operations to refresh statistics. If the statistics on a table are locked, and it is not a Global Temporary Table, then the wrapper package will force collection and update of statistics on the table (previously it suppressed gathering of statistics on tables with locked statistics).

However, when the Application Engine program completes, any statistics collected on those temporary tables are no longer needed. Worse, the statistics refer to data that will be deleted and replaced by some future program, and if the table were not reanalysed, the statistics would be misleading, and could cause the database to produce an inappropriate execution plan. Some temporary records are shared by multiple programs, so you cannot guarantee that statistics will always be refreshed when the table is next used.

When an Application Engine program completes successfully, or when the process request is cancelled, specific instances of temporary records that were allocated when the program began are deallocated by deleting the row from PS_AETEMPTBLMGR. Therefore, I propose the following trigger that will delete the statistics for that record when that row is deleted.

NB: The trigger must use an autonomous transaction because dbms_stats also commits its updates.

You can test the trigger like this: First I will populate the control table with a dummy record, and collect statistics

INSERT INTO ps_aetemptblmgr
(0,'TL_EXCEPT_WRK',24,'PS','Wibble','TL_TIMEADMIN',sysdate,' ', 1,0)
execute dbms_stats.gather_table_stats(ownname=>'SYSADM',tabname=>'PS_TL_EXCEPT_WRK24',force=>TRUE);

column table_name format a18
SELECT table_name, num_rows, last_analyzed
FROM user_tables where table_name = 'PS_TL_EXCEPT_WRK24'

------------------ ---------- -------------------
PS_TL_EXCEPT_WRK24 0 14:36:12 06/04/2009

Now I will delete the row, and the trigger will delete the statistics for me.

DELETE FROM ps_aetemptblmgr
WHERE process_instance = 0
and curtempinstance = 24
and recname = 'TL_EXCEPT_WRK'

SELECT table_name, num_rows, last_analyzed
FROM user_tables where table_name = 'PS_TL_EXCEPT_WRK24'

------------------ ---------- -------------------


Larry said...

I have one doubt, is there a way to set particular timeframe to purge temporary tables ?

Actually I was going thru interview questions related to PeopleSoft at following website - www.itwisesolutions.com/PsftQuiz.html and found lot of tricky questions.


David Kurtz said...

I think that temporary tables are automatically purged by AE when they are allocated to an application engine instance. It is not done when the program ends, I think, because then the data is available for debug.