Missing SQL in DBA_HIST_SQLSTAT

Has anyone checked into the accuracy and reliability of AWR SQL stats?  From 
checks I've done it appears that a lot of SQL statements are not getting 
captured in AWR snapshots.

Here's our config: 4-node RAC, Oracle 10.2.0.2, RH 4.x, 30-minute AWR snapshots.

We've left TOPNSQL as "DEFAULT", which in our case should be enough:

SELECT topnsql
  FROM sys.wrm$_wr_control;

           TOPNSQL
------------------
        2000000000

This means that the first 2 BILLION SQL statements per category will be 
selected (seems rather excessive!).  Yet I ran a few checks where I compared 
(GV$SQL.LAST_ACTIVE_TIME - snapshot interval) to the MAX(end_interval_time) for 
snapshots (all by SQL_ID) and found over 1600 statements that are executed yet 
no updates are captured by AWR.

As a double check, I reviewed data in DBA_HIST_ACTIVE_SESS_HISTORY and found 
that 1 of the 1600 statements from above is executed multiple times per day, 
yet the last DBA_HIST_SQLSTAT snapshot it's in is from 4 months ago.

Has anyone else seen this type of thing and/or done detailed checking on the 
accuracy of AWR SQL data?

BTW, I tried tracing the snapshot activity and can't get past what's done to 
populate internal objects X$KEWRSQLIDTAB and X$KEWRSQLCRIT.

Dave Herring  | DBA
Acxiom Global Technology Solutions   

630-944-4762 office | 630-430-5988 cell | 630-944-4989 fax
1501 Opus Pl | Downers Grove, IL, 60515 | U.S.A. | www.acxiom.com
Service Desk: 888-243-4566, https://servicedesk.acxiom.com, GSCA@xxxxxxx



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