Problem with vhand process

[Rene Mendez_4]

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 ?

[Sanjay_6]

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

[Jeff Schussele]

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

[Rene Mendez_4]

My data base is only row device,

Modify dbc_max_pct is only with file system ?

[Johan Lorimier]

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

[Franky Leeuwerck_2]

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

[Navin Bhat_2]

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.

[Sarvesh A Dhuri]

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.

[Navin Bhat_2]

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.