AIX

Guy's

This is our page space , i want some information about page space and I want the good way to how to increase the page space and what's the recommended page space that need to be configured


Page Space Physical Volume Volume Group Size %Used Active Auto Type Chksum

hd6 hdisk0 rootvg 512MB 19 yes yes lv 0

Memory performance

Paging space

Is it enough?

double size of memory has always been a good setting to me

but just up to 20gb

I don't give a system 80gb swap, with 40gb of memory



to increase, check out the mkps command, as well as swapon and swapoff

Default:
If real memory is less than 256 MB, paging space is two times real memory.
If real memory is greater than or equal to 256 MB, paging space is 512 MB.

First off, i ask you to discontinue whatever you do that causes the excessive formatting of your posts. Half of your text is various tags.

Paging space is used as a memory-extension in cases your running programs (want to) use more memory than you actually have. In times gone memory was very expensive and it was a good idea to make it look like a system has more memory available than it actually had. Today memory is cheap and one tries to avoid paging (swapping) at all costs.

Still it won't hurt to have some virtual memory available for extraordinary situations (diskspace is even cheaper than memory and hence wasting some of it matters even less), but in day-to-day operation the system should be able to do without using this swap space (paging space) at all costs.

Having said this, the following is a rule-of-thumb suggestion and in no way an exact analysis: I would start (in a system with a today typical memory size of 4-8GB) with 2-4GB of paging space for starters and watch carefully. If this paging space i used quite often you might want to increase the memory size, depending how often paging (that is: transfer of memory content to/from the paging space) really happens.

There are processes which "sleep" in memory for the whole day, get swapped out, start to work once a day and go back to sleep again. In this case you would see some paging space consumption, but not actual paging going on (save for the process waking up and getting swapped out again some while later). In such a case you might want to increase the paging space size to still have the 2-4GB in contention but leave the memory size as it is.

Monitoring the paging space

There are two distinct areas to watch when monitoring the paging space: the paging space consumption and the paging activity itself. Use

Code:

lsps -a

to watch the consumption in percents. Do this regularily, like every 10 minutes for starters, writing the results in a file. Once you have gained some knowledge about the system you can increase the sampling rate and only execute the command every hour or even only once or twice a day. Try the following as a basis for some monitoring script:

Code:

while : ; do
     lsps -a >> /path/to/lsps.monitor."$(date '+%Y%m%d')"
     sleep 600                 # take snapshot every 600sec=10minutes
done

Watching the actual paging activity is done similarily with "vmstat", but vmstat already works contiually, so you don't need any loop:

Code:

vmstat -Itw <interval_in_seconds> >>/path/to/vmstat.monitor."$(date '+%Y%m%d')"

Notice the part titled "page" and especially the "pi" (page in) and "po" (page out) columns. These should be mostly zero. Like with "lsps" start with some small sampling rate which you can increase once you know how the system performs in general.

You will want to read up about performance tuning and monitoring in general. There are some pretty informative threads here, off the top of my memory:

AIX 5.2 performance question
https://www.unix.com/aix/45180-hard-d...y-command.html
AIX : 0 pages swappes

... and probably a dozen more I'm not aware of.

I hope this helps.

bakunin

Hi,

The implementation of the policy page-space is very complicated to make it real effective.
Sometimes, with some hardware configurations recommended the development of several page-space, one page on each local disk. Then the operations on the page space are actually performed in the area of the disk cache, avoiding a physical write to disk.
For example, a large page swap disk causes the transmission swap-memory block / limit the availability of disk space. IBM does not allow the page to swap more than 20% of disk capacity.
As for the price of IBM introduces newer SSDs. Oracle Database already knows how to use it.
As for page space even remember the versions of AIX 4.x
For example, NFS needs a lot of page space. What if almost all the disk space is available via NFS.
Applications with databases, CATIA want most memory and swap.
The real-time systems would be ideal that the system did not benefit from the swap, but it's just an idea.
Each disk operation is extremely longer time than in memory, cpu very speed, therefore, multi-tasking.
I admit that given by me default values are sometimes inadequate.
Often better to create a second page-space on the second disk than to increase an existing one. Often better to create file page-space then create or increase page-space. You can deactivate file without reboot!!!!
Bye

How to increase the page space to 1GB and is this recommended ?