Re: Guidelines for avoid Bind Variable Peeking behavior
- From: troach@xxxxxxxxx
- To: roberto_veiga@xxxxxxxxx,oracle-l@xxxxxxxxxxxxx
- Date: Sun, 31 May 2009 14:19:20 +0000
Have you considered not using binds for certain statements? How many times is
the query executed?
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-----Original Message-----
From: Roberto Veiga <roberto_veiga@xxxxxxxxx>
Date: Sun, 31 May 2009 07:14:16
To: <oracle-l@xxxxxxxxxxxxx>
Subject: Guidelines for avoid Bind Variable Peeking behavior
I am facing a lot of problems with bind variables because the access plan is
changing and a critical performance problem occurs.(I have already posted a
question "Histogram worthwhile" here at Oracle-l). I am suffering the "bind
variable peeking" behavior.
My customer is very disapointed about this "feature" of Oracle and he is asking
me what to do to avoid this behavior.
We have already tried to remove histograms and the situation become worse.
I have proposed him to focus on the most critical process and put some hints to
freeze the plan.
But the processes work with a lot of procedures with a lot of statements. So I
need to define a method to focus only in the queries with most change to have
this problem.
I can use Stored Outlines (Plan Stability) but I have a *lot of* queries and I
need a fast way to configure those queries.
I am thinking use Sql Profiles but I need a fast way to use this with a lot of
queries and I really dont know if this approach is going to resolve the
changing plan problem.
I am thinking using this points to focus only in a few potential problem
queries:
-Statements with Bind Variables
-Columns with Skewed distribution
-Statements with more than 5 tables join
-Tables with many rows (500k or more)
-Access plan using Hash Join
Is this a good approach to identify queries that can have the plan changed?
We are having a great pressure to minimize this situation.
Thanks in advance,
Roberto Veiga
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