I think you can trust the STAT lines in a SQL trace file to give you
accurate information about what execution plan *did* take place. The test I
would suggest is to compare the information in these lines to what EXPLAIN
PLAN shows you. You'll need to look at the raw trace data, though, because
tkprof doesn't always convert STAT lines into a correct execution plan.
 

Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com

Upcoming events:
- Hotsos Clinic 101, Apr  8-10 Chicago


-----Original Message-----
Sent: Thursday, March 20, 2003 2:24 PM
To: Multiple recipients of list ORACLE-L

Hello,

Heres a question to ponder. While tuning a SQL statment for a user I noticed
that the explain plan from SQL Analyze was not the same plan that was found
when I used OEM Top Sessions (9.2.0.1) upon executing to collect execution
stats.  Database is on HP/UX 11 version Oracle 8.1.7

The stats were not "stale" yet. Monitoring is on for the tables in the
query. The query would actually never return. I suspected that the stats
were a bit off so I ran new ones and then SQL Analyze displayed a different
explain plan and the plan reteived from top sessions while the SQL was
running matched.

My question is is the Explain Plan and estimate or is the actual plan. I
suspect that when an explain plan is created it uses statistics and the
optimizer to determine the estimated plan and cost. However when the SQL is
actually executed I suspect that a different plan may be generated as actual
execution begins....or am I just wacked.

Either way the statistics when run created a proper plan that worked fine.
But I wonder why the difference in plans...

Brad O.


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