We have 4 CPUs in the database server and we are trying to make use 2 of them for SYBASE use.
See code 1 for the setting.
But when I checked the process running on the server, there's only one "dataserver" process.
and when I run sp_monitorconfig "max online engines" it shows that Max_Used == 1. See code 2.
When I run select * from master..sysengines, it only shows engine 0.
How can I activate sybase to use more that 1 engine?
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Obviously, that's the first thing that I did.
There's a lot of logs in there, so this is the error that might be related.
"engine 1, os pid 26168 exited"
"Process 26168 exited with status 1"
"Task with kpid 0 running on failed engine"
"online failed"
"Warning: Cannot set console to nonblocking mode, switching to blocking mode."
And this error came out when I try to use dbcc tune(cpuaffinity, -1, 'on')
"This platform does not support cpu affinity."
Thanks.
I'm using Sybase ASE 15.
cat /etc/redhat-release :-
Red Hat Enterprise Linux AS release 4 (Nahant Update 4)
It seems that sybase is using all 4 processors. I just realize that high cpu usage is switching between CPU 1,2,3 and 4. But it seems that whenever 1 CPU is use by sybase, the others are more likely idle.
What you're describing is correct and expected. Sybase does not have a hard affinity of dataserver engines to operating system processors, so an engine can totally hop around processors. This is what dbcc tune (cpuaffinity [...]) alters.
But there is a soft affinity, in that generally the same engine will tend to run on the same processor. This is not actually a Sybase measure but an OS measure, trying to minimise context switches at the CPU level which can be relatively costly due to L1 and L2 cache misses when moving a process to a new CPU. (I think that was the explanation, I didn't follow it entirely when it was explained to me.)
But within Sybase we do (sort of) have task affinity. If there are fewer runnable spids than we have engines, the same spid well tend to remain on the same engine. It doesn't have to though (unless constrained by the LPM features) except for network I/O which will always be performed by the same engine for the life of that connection.
I'm a bit puzzled that you weren't seeing multiple lines in sysengines though. If that's still the case, have a look at the ASE 15.0.x "Release Bulletin" manual (you still didn't tell us the exact version BTW) and confirm you have all the Linux patches and kernel settings needed for Sybase to run correctly.
Oh, I hadn't noticed there were a couple of specific questions not answered:
> And this error came out when I try to use dbcc tune(cpuaffinity, -1, 'on')
> "This platform does not support cpu affinity."
Yep, that's only available on some platforms. There may be RHEL features that achieve the same end, although really there's usually little benefit these days to binding ASE engines to CPUs as the OS does a pretty good job of maintaining soft affinity anyway.
> It seems that sybase is using all 4 processors. I just realize that high cpu usage is switching between CPU 1,2,3 and 4.
Are you getting multiple engines starting up now?
> But it seems that whenever 1 CPU is use by sybase, the others are more likely idle.
That is what we'd expect to see for a workload that was largely single-threaded, like a batch job or a system that isn't being used by many concurrent engines.
BTW that error about engines failing is a known issue and I was right, it has to do with the environment not being properly setup for Sybase. You need to run:
set -s unlimited
prior to launching ASE. Suggest you put it in the Sybase .profile, log out and log back into the box, then restart ASE.
This sets an unlimited stack size, without which the additional engines can't attach to the shared memory of the first engine brought online. There are other issues that can cause this error too, but without the full errorlog it's not possible to say which is which. (I appreciate you were probably trying to limit the size of what you were attaching but there's a reason I asked for the full errorlog sequence... :) )
Anyway, good luck!
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by: bleach77Posted on 2009-08-03 at 00:51:12ID: 25002458
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