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Re: Why do i see so high "Curs/Sess" in statspack?

From: Brian Peasland <oracle_dba_at_nospam.peasland.net>
Date: Mon, 26 Jun 2006 19:00:11 GMT
Message-ID: <J1HE4H.Dzz@igsrsparc2.er.usgs.gov>


lasse.jenssen_at_gmail.com wrote:
> My "open_cursors" is set to 1000. Why do i see so high value for
> "Curs/Sess" in statspack, and what effect could this have on
> performance?
>
> STATSPACK report for
>
> DB Name DB Id Instance Inst Num Release RAC Host
> ------------ ----------- ------------ -------- ----------- ---
> ----------------
> xxxxx xxx xxx xxxxxxx 1 10.1.0.4.0 NO
> redhat-db
>
> Snap Id Snap Time Sessions Curs/Sess Comment
> --------- ------------------ -------- ---------
> -------------------
> Begin Snap: 535 26-Jun-06 10:47:30 156 7,047.1
> End Snap: 536 26-Jun-06 11:17:35 155 7,123.3
> Elapsed: 30.08 (mins)
>
> Regards
> Lasse
>

OPEN_CURSORS defines your maximum number of *open* cursors at any one time, across all sessions in your instance.

The Curs/Sess is showing the number of cursors per session, open and closed. If I issue a query, that is one cursor. That query may actually open up other cursors for recursive SQL, etc. When that query is done processing, the cursor is closed. Another query will open other cursors. All of these will count towards Curs/Sess. This value could very well be higher than OPEN_CURSORS and by itself is not indicative of a performance problem.

HTH,
Brian

-- 
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Brian Peasland
oracle_dba_at_nospam.peasland.net
http://www.peasland.net

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Received on Mon Jun 26 2006 - 14:00:11 CDT

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