RE: session_cached_cursors and ora-07745
- From: "Mohan, Ross" <RMohan@xxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 15 Mar 2005 22:36:08 -0000
test/dev instance...7445...."other 920 databases" (which full =
versions?)...due to....what?
Usually there's *something* in the u/bdump traces that indicates root =
cause. Is there some=20
reason you've assumed the cursor caching is causal (as opposed to =
coincident)?
Some questions that come to mind.
- what are full versions of other DBs?
- any other trace files concurrent?
- when was session_cached_cursors changed on the test/qa box?
- how long was parameter in play before the 7445?
- was the instance under steady, sporadic, episodic (i.e. "rollout") or =
unusual load?
- have you set the parameter down or off (assuming, since this is =
test/qa, you have that
option)
- can you 'instrument' your apps to track cursor usage?=20
- is statspack running in there, and can you tracked current/cumulative =
open cursors
over time?
I'd say "try truncating the URL_PAGES table" but I don't know if you =
have the Oracle
High Performance Option (OHPO) installed. :-)
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx =
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Paul Drake
Sent: Tuesday, March 15, 2005 5:10 PM
To: robyn.sands@xxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: session_cached_cursors and ora-07745
From the readme from 9.2.0.5 patchset for win32:
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Oracle9i Database Server
Patch Set Notes
Release 2 Patch Set 4 Version 9.2.0.5.0 for 32-Bit Windows March 2004=20
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.=20
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
From that, I thought that it was proper to set
|open_cursors|=3D|session_cached_cursors|
where |parameter| =3D 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@xxxxxxxxx> wrote:
> Hello all,
>=20
> One of my test/dev instances went belly up yesterday morning with=20
> ORA-07445 errors in the alert log. I've the the database back but I=20
> ran across a doc on metalink (Note:274496.1) that indicates using=20
> parameter session_cached_cursors should not be used with version=20
> 9.2.0.5 and up.
>=20
> This database is 9.2.0.6 / HP-UX 11.23. I've been selectively using=20
> 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=20
> and/or heard that this param should not be used?
>=20
> tia ... Robyn
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>=20
--=20
#/etc/init.d/init.cssd stop
# f=3Dma, divide by 1, convert to moles.
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