IDS Forum

RE: Onbar uses sqlexec threads or???

Posted By: Sebastian, Norma J.
Date: Tuesday, 27 July 2004, at 8:51 a.m.

Hello everyone,

Thanks to all who responded, clarifying the onbar threads.

Status/resolution(?) to my problem submitted below...
1) The botched up SAP Kernel patch had nothing to do with the DB perf
problem.
2) onbar may have it's own buffer cache (310kb in my case), but it
appears to have been dancing in the regular buffer cache (1.6GB in my
case) and have caused foreground writes.
3) CCFLAGS, although not thought to have been involved in this
particular problem as it's traditional "tell tale signs" were not seen,
was nonetheless the answer, or at least it appears so.... (one good
backup may not make a trend..)


On a hunch, I turned on CCFLAGS in production last night. Worked like a
charm. The DB level 0 tape backup ran in record time (increased speed
IS a reported result/purpose of CCFLAGS), and I did not have long
checkpoints (not an expected result for CCFLAGS in my case).

Thanks to you all for your theories and support.

....And if you haven't been to the Informix internals class... .. GO...
It's very very worthwhile.

Have a great day,
Norma Jean



-----Original Message-----
From: Sebastian, Norma J.
Sent: Tuesday, July 20, 2004 2:48 PM
To: ids@iiug.org; sapmix@iiug.org
Cc: Sebastian, Norma J.
Subject: Onbar uses sqlexec threads or???

Hi all,

Onbar questions regarding the buffer cache..... (I'm using IDS
7.31.FD6X3 on Sun Solaris 64 bit, with Veritas Netbackup for Onbar)

My onconfig :
BUFFERS 800000
BAR_MAX_BACKUP 12
BAR_RETRY 2
BAR_NB_XPORT_COUNT 10
BAR_XFER_BUF_SIZE 31

Would this be ? :
800,000 buffers * 2048 byte pages (sun solaris 2.7) = 1.6 GB
when a backup runs, it will allocate 10 of the 800,000 buffers for
data transport, and these buffers will be 31 KB (therefore 10 * 31 kb =
310 kb)? So when a backup runs, I am using 310 KB of the 1.6 GB to
handle the backup?, (310 KB out of 1.6 GB is a drop in the bucket)

Am I thinking correctly on this?

If onbar is just another unix process, does it use sqlexec threads as
worker bees for the backup?

I am wondering because we are on SAP. Last Saturday I did an Informix
upgrade (731fc6x2 to 731fd6x3) and the SAP admins did an SAP kernel
patch. That night, the onbar backup started, and the checkpoints went
crazy.... From an average of 10 seconds to an average of 200+ seconds.
Also the foreground writes were shooting through the roof.
We discovered a goof up in the SAP kernel patch, that we hope, once
fixed will fix the issue. None of my other similarly upgraded systems
are performing badly (but the SAP kernel patch was not goofed up on
those systems).

I know sqlexecs do foreground writes, and I know they are bad. (again,
I am optimistic the SAP kernel goof will fix that).
But I got to wondering if onbar could also have been doing some
foreground writes... .. So I'm thinking if onbar does not use sqlexec
threads, it would not have been involved in the foreground writing...
Therefore the foreground write mess and badly performing use of the
Informix buffer cache was predominantly caused by the sapr3 (SAP user)
connections, not the onbar connections....

It may be a long shot, but it's all I got for now....

If anyone can help me understand this, I'd appreciate it, Thanks, NJ

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