topic Re: Problem with vhand process in Operating System - HP-UX

Problem with vhand process

Rene Mendez_4 — Tue, 27 Apr 2004 15:00:49 GMT

Model: rp7405
Memory: 8GB
CPUs: 4
Data Base: Sybase / 2 instance

Problem: Process vhand use all CPU and server stop.

I attach the top output

The problem is software o hardware ?

Re: Problem with vhand process

Sanjay_6 — Tue, 27 Apr 2004 15:04:58 GMT

Hi,

Reduce the "dbc_max_pct" kernel parameter value to 10%. This is probably set to a higher value at present, probably 50% or something.

If you change this paramter, you'll have to rebuild the kernel and reboot.

Hope this helps.

Regds

Re: Problem with vhand process

Jeff Schussele — Tue, 27 Apr 2004 15:08:41 GMT

Hi Rene,

If vhand is that active you're probably memory starved. As Sanjay suggest check the dbc_max_pct & dbc_min_pct & lower them to around 10 & 5 respectively. If theye're already down there then you either have to install more memory & reduce memory pressure.

Rgds,
Jeff

Re: Problem with vhand process

Rene Mendez_4 — Tue, 27 Apr 2004 17:12:18 GMT

My data base is only row device,

Modify dbc_max_pct is only with file system ?

Re: Problem with vhand process

Johan Lorimier — Tue, 27 Apr 2004 17:40:38 GMT

Hi,

dbc_max_pct refer to the max percent of memory the system will setup as buffer cache. Even if you database use RAW device, not all part of your application used raw dev, the binary and the libs are most of the time in normal filesystem. If your parameter is already setup to 10 or less then you have to reduce the sga of your database.

Johan

Re: Problem with vhand process

Franky Leeuwerck_2 — Wed, 28 Apr 2004 03:44:30 GMT

Hi,

I am not familiar with Sybase but you can have a memory leak.
In that case, stop the DBMS instances, reboot the machine, and restart Sybase.

If, after a reboot you see rather soon, the vhand process taking all CPU resources again, then probably your DBMS cache tuning is set too large. In this case, lower your dbms cache configuration and restart the dbms.

Regards,

Franky Leeuwerck

Re: Problem with vhand process

Navin Bhat_2 — Wed, 28 Apr 2004 10:22:01 GMT

Hello Rene,
The fact that vhand is active means that your system is facing severe memory pressure. Please send us the output of kmtune from your system. If you feel the kernel parameters are tuned right like dbc_max_pct (use sam too) then check for other causes, maybe memory leaks in applications or just plain overload and you need to add more memory because you may have added more users hence more processes.

Also please check if you have the latest patch bundles for vm.

When you have vhand become extremely active you could experience system hangs or system becomes very unresponsive.

Re: Problem with vhand process

Sarvesh A Dhuri — Wed, 28 Apr 2004 11:30:37 GMT

Hi

vhand process comes into picture only when systems various process requires more and more memory , i guess by changing dbc_max_pct and dbc_min_pct wont sort out the issue, the best thing is to upgrade the memory.

Re: Problem with vhand process

Navin Bhat_2 — Wed, 28 Apr 2004 12:56:59 GMT

dbc_max_pct and dbc_min_pct can and will make a difference if they have been set too high even though you are using raw devices for the database. You can result in leaving insufficient memory for your applications. There are other filesystem activities on the system that can use buffer cache like copying files across, etc...

Once again please post the kernel tunables and we can assist you better.