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тАО04-17-2003 12:29 PM
тАО04-17-2003 12:29 PM
Ted
Solved! Go to Solution.
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тАО04-17-2003 12:59 PM
тАО04-17-2003 12:59 PM
Re: HPUX Free Memory
It's not so much how *much* memory is free. It's about the % of free memory pages.
vhand & sched are the processes that watch the free page % & initiates actions based on that value.
Here's a good doc on how & why vhand & sched do what they do.
http://www.docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/5965-4641/5965-4641_top.html&con=/hpux/onlinedocs/5965-4641/00/00/11-con.html&toc=/hpux/onlinedocs/5965-4641/00/00/11-toc.html&searchterms=vhand&queryid=20030417-145550
HTH,
Jeff
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тАО04-17-2003 01:05 PM
тАО04-17-2003 01:05 PM
SolutionThere is only one limit you can take in this scenario, especially if you have to justify the purchase of new memory - the kernel counter desfree. The is the desired amount of free memory the OS needs to prevent paging to the swap devices, which will have a negative impact on performance. To find this value use:
# echo desfree/D|adb -k /stand/vmunix /dev/kmem
This will report the number in 4k pages. I believe it defaults to 1/64 (or 1/32??)of physical memory on a system of your memory capacity. Also use:
# swapinfo -tam
To check for any usage of the swap devices at peak usage. This in itself may be justification of the need to add more memory if performance is critical on your server. This should also give you a guide on how much memory to add.
Regards,
James.
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тАО04-17-2003 01:09 PM
тАО04-17-2003 01:09 PM
Re: HPUX Free Memory
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тАО04-17-2003 05:38 PM
тАО04-17-2003 05:38 PM
Re: HPUX Free Memory
On the other hand, if po is 100 or higher for long periods of time, then you are indeed short of RAM and may need to increase to 8Gb. The reason you can pile so many processes beyond the limits of RAM (and not see a slowdown) is that a lot of the processes are idle while they wait for some keyboard responses. These interactive tools are perfect for low memory systems since they can be paged out to swap and no one will notice.
On the other hand, if the 6 instances of Sybase significantly exceed the available RAM, then page-out rates will soar and overall performance will seriously degrade. The fix is easy though: add a lot more RAM. You DBAs will love the additional RAM as it will improve response time as they ask for more...
Bill Hassell, sysadmin