Difference between revisions of "Maximo - Tuning Oracle parameters shared cursors"

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Category: Oracle
 
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Revision as of 17:21, 15 January 2012

Maximo - Tuning Oracle parameters shared cursors [edit] This section covers the Oracle Cursor Sharing parameter and why Maximo wants 'SIMILAR'.

Check out the following:

Ask Tom: On Sharing, Splitting, and Deleting

From the Ask Tom Article above you get:

The CURSOR_SHARING parameter can have one of three values:

   EXACT - This is the default setting. With this value in place, the query is not rewritten to use bind variables.
   FORCE - This setting rewrites the query, replacing all literals with bind values and setting up a one-size-fits-all plan—a single plan for the rewritten query. I'll demonstrate what that implies in a moment.
   SIMILAR - This setting also rewrites the query, replacing the literals with bind variables, but can set up different plans for different bind variable combinations. This last point is why CURSOR_SHARING=SIMILAR might reduce the number of plans generated. Because multiple plans may be generated, the setting of SIMILAR may or may not reduce the number of actual plans you observe in the shared pool 

You will pay a 3-5ms penalty (depending on how well tuned your Oracle system is!) on each query to the database while in 'EXACT' and I've never tested 'FORCE'.

IF your running 10.2.0.1 or 10.2.0.2 you will have (or should) use 'EXACT' until you can get your system patched to at least 10.2.0.3 (IBM Recommended) or 10.2.0.4 (Not IBM Certified yet as far as I know).

See the following article(s) for more related information:

   Maximo - Tuning Oracle parameters session cached cursors 
   Oracle - JDBC Drivers release 10.2.0.1.0 Downloads 

--wkh 05:13, 5 March 2009 (UTC) Category: Oracle