Re: DB CPU is much lower than CPU Time Reported by TOP SQL consumers
- From: Marcus Mönnig <mm@xxxxxxxxxxxxxxxx>
- To: Oracle Mailinglist <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 13 Nov 2012 20:32:52 +0100
You are likely seeing double counting in the SQL CPU section.
Looking at the execution counts, it might well be that e.g. the fourth SQL
statement is called from within the first SQL statement. The other
execution counts also kind of match to each other. Of course this is
nothing but an educated guess and you would need to look at the (PL/)SQL
code behind these SQL hash values to verify.
Is the system using scheduler jobs? In that case the anonymous (Oracle
internal) PL/SQL code that calls the PL/SQL job action will collect all the
CPU time and the called PL/SQL job action might e.g. have one SELECT
statement that actually eats the CPU and the CPU time is also counted
towards this statement.
Another case is a construct like:
Statement1: SELECT pl_sql_function(column) from ...
Where pl_sql_function is a PL/SQL function that returns a value based on
another SQL Statement (Statement 2) and that is executed for each row
returned by Statement 1.
Both the CPU times reported for Statement 1 AND 2 will include the CPU
times burned by Statement 2.
Marcus
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