Why does _no_or_expansion affect Execute time rather than Parse time?

Howdy,

I have recently tuned a set of queries in a Siebel implementation on Oracle 10gR2. Several queries had exceptionally high "Execute" time reported by tracing the 10046 event. The execute time was eliminated by changing the _no_or_expansion parameter to TRUE. We are aware that this may affect other queries. The query plans were exactly the same with the parameter set to TRUE as it was when set to FALSE. The only difference is the Execute time cut from 22+ seconds to less than one second.

My question is - why was this time reported as Execute rather than Parse? Shouldn't the contemplation of what plan to run be considered parsing - and then actually executing the plan be executing? Wouldn't or expansion be part of contemplating what plan to run?

Thanks in advance,

Joe    

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