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Date: Sun, 4 Feb 2007 09:48:15 -0600
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In addition to the advice already provided, I can offer the following:  

  1. I assume that you are on Siebel 7.8 or higher with Oracle 9i or higher. Lower versions of either are only supported in RBO.
  2. Siebel was very well tuned to run in the RBO. Its vanilla index structure and recommended instance settings (almost) always resulted in the right plan for the queries it generates. Sometimes "performance issues" arise after an upgrade because things that used to be un-necessary with the RBO are now very important with the CBO - such as properly generating statistics.
  3. In that sense, treat this as an Oracle instance with a schema that someone else created - not as a black box provided by Siebel. Use statspack, trace sessions, capture the SQL and run it via command line in a test instance to determine what the "right path is" and experiment with session parameters that way. Don't forget the various alter session statements that Siebel runs at the beginning of each session.
  4. Most problems can be fixed by creating or dropping indexes. This was true with the RBO and is true now. Some indexes are present for specific application screens that most sites do not use.
  5. We have found inappropriate plans that we fixed by adjusting OPTIMIZER_INDEX_COST_ADJ and OPTIMIZER_MAX_PERMUTATIONS. The settings vary and you should test them yourself.
  6. We have also found what I call the "FIRST_ROWS10 rock and a hard place." Siebel sessions are altered to use FIRST_ROWS10 - apparently to help out with "sorted all views" and "pop up applets" in the vanilla application that provide the user a list of all of a particular business component (contacts, accounts, addresses, etc.) in the system. The wisdom of this application design aside, this amounts to an order by on some highly select columns with some filters on not very selective columns. FIRST_ROWS10 speeds this condition up considerably. Unfortunately, it also slows down the similar query run later with a highly selective query - such as one that was executed during the login process on version 7.7... We have also used stored outlines to address this problem.
  7. This is not to say that stored outlines are always the answer. If you have a strong DBA capability and sufficient time to test the impact on the rest of the application, then you "should" be able to solve this by managing statistics and optimizer settings.

Bottom line - there is no "silver bullet" setting you can take from the list aside from that "others have successfully made the transition." Just treat this like any other performance problem.  


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Received on Sun Feb 04 2007 - 09:48:15 CST

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