02-12-2006
I don't use AIX and I do not understand the commands you used except for vmstat. But I can make a few general comments. It is not clear from your post what effect you would like to have on your system. Running out of swap would be a disaster. You would get messages like "can't fork", "out of memory", etc. Many programs do not handle errors like these very well. The box well might crash or lock up and a reboot would be needed to get things going again. Running out of swap means that you are out of virtual memory. Running out of physical memory is not good but perhaps not a disaster. If vmstat showed you a scan rate of 3000+, you clearly had been out of physical memory for some time. Generally, the box can run in this state, but with a performance impact. If you want to check your swap to ensure that were not close to a disasterous out-of-swap condition, that is a great idea, and I hope some AIX expert comes along who knows those other commands you used. But if you want to address that performance problem, you will need more memory. You may be able to make a modest impact on the severity of the performance problem by distributing your swap across more disks. But adding more memory can make the performance problem go away.
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LEARN ABOUT HPUX
swapmem_on
swapmem_on(5) OBSOLETE swapmem_on(5)
NAME
swapmem_on - OBSOLETE kernel tunable parameter
DESCRIPTION
The tunable is obsolete. Processes will always be allowed to use pseudo-swap space if it is available.
In previous versions of HP-UX, system configuration required sufficient physical swap space for the maximum possible number of processes on
the system. This is because HP-UX reserves swap space for a process when it is created, to ensure that a running process never needs to be
killed due to insufficient swap.
This was difficult, however, for systems needing gigabytes of swap space with gigabytes of physical memory, and those with workloads where
the entire load would always be in core. This tunable was created to allow system swap space to be less than core memory. To accomplish
this, a portion of physical memory is set aside as "pseudo-swap" space. While actual swap space is still available, processes still
reserve all the swap they will need at fork or execute time from the physical device or file system swap. Once this swap is completely
used, new processes do not reserve swap, and each page which would have been swapped to the physical device or file system is instead
locked in memory and counted as part of the pseudo-swap space.
WARNINGS
Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parameter values. After installation,
some tunable parameters may no longer be at the default or recommended values. For information about the effects of installation on tun-
able values, consult the documentation for the kernel software being installed. For information about optional kernel software that was
factory installed on your system, see at
AUTHOR
was developed by HP.
Tunable Kernel Parameters swapmem_on(5)