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Re: session_cached_cursors and ora-07745

Paul Drake

2005-03-15

Replies:
From the readme from 9.2.0.5 patchset for win32:

==================================================================
Oracle9i Database Server
Patch Set Notes
Release 2 Patch Set 4 Version 9.2.0.5.0 for 32-Bit Windows
March 2004


PL/SQL Cursor Caching

Prior to release of the 9.2.0.5.0 patch set, the maximum number of
cursors that could be cached for fast lookup by PL/SQL was bounded by
the value of the init.ora parameter open_cursors. If you currently
have open_cursors set to a high value (for example, greater than
1000), it is likely that this is causing large numbers of PL/SQL
cursors to be cached in the shared pool. This could lead to issues
with memory management, frequent reloading of library cache objects
and ORA-04031 errors.

Patch set 9.2.0.5.0 alleviates the issue by changing the init.ora
parameter which determines the upper bound for PL/SQL cursor caching
from open_cursors to session_cached_cursors.

Most users will not need to modify the value of either of these
parameters. If you already have session_cached_cursors set to a value
greater than the open_cursors parameter, then this change will have no
performance impact upon your system.

However, if you have session_cached_cursors set to zero, or set at a
value significantly lower than the open_cursors parameter, and you are
concerned that PL/SQL cursors need to be cached for optimal
performance, then you should ensure that the session_cached_cursors
parameter is increased appropriately.

This issue is bug number 3150705.
==================================================================

From that, I thought that it was proper to set
|open_cursors|=|session_cached_cursors|
where |parameter| = value (aka magnitude or scalar).

The metalink note makes it clear to me that this is overkill.
From this, it looks like I'd revert session_cached_cursors back to 100
and leave open_cursors at 255 like I did back in 9.2.0.4.

I do recall having a series of ora-4031 issues for a db after it went
from 8.1.7 to 10.1.0.3.
This could help to explain that.
(the system state dump run while throwing the 4031s never completed as
after 40 min we just bounced the db inst).

Paul

On Tue, 15 Mar 2005 16:50:58 -0500, Robyn <robyn.sands@(protected):
> Hello all,
>
> One of my test/dev instances went belly up yesterday morning with
> ORA-07445 errors in the alert log. I've the the database back but I
> ran across a doc on metalink (Note:274496.1) that indicates using
> parameter session_cached_cursors should not be used with version
> 9.2.0.5 and up.
>
> This database is 9.2.0.6 / HP-UX 11.23. I've been selectively using
> session_cached_cursor with other 9.2.0 databases but this is the first
> db that I've seen these errors on. Has anyone else seen this happen
> and/or heard that this param should not be used?
>
> tia ... Robyn
> --
> http://www.freelists.org/webpage/oracle-l
>


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