Originally posted by: SystemAdmin

Dear,

How can i change/enlarge the virtual memory on AIX? where can i find the step?

TKS
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Originally posted by: dpearman

If you are using a version prior to AIX5L you will need to use the /usr/samples/kernal/vmtune -P [i]value[/i] command to set the MAKPERM parameter. Versions 5L and later use /usr/sbin/vmo -P [i]value[/i] command. To check the current value run /usr/bin/vmstat command. Under MEMORY the AVM category shows your ACTIVE VIRTUAL MEMORY.

[b][i][u]BEWARE[/u][/i][/b]
Changing your virtual memory may cause other unwanted problems, so tweak it a little bit at a time and watch the results over a couple of run cycles through heavy traffic to see if it is going to cause you more problems. You can read the man pages on the vmtune or vmo commands to get a better understanding of the commands and possible consequences. You might need to tweak the [i] maxpgahead (-R), maxfree (-F), or maxrandwrt (-W)[/i] parameters to get better response time after you tweak the virtual memory.

Now my disclaimer: I am not tech support, only another user in the industry and only offer this suggestion in good faith.
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Originally posted by: nagger

Hang on I don't think the previous post answers the question at all - that answered "How do I tune VM?" question.

VM is backed up via the paging space.
To show and change the paging space I use: smitty pspg
Yes, you can use the AIX commands directly but I find the smitty way simpler.
For example adding a paging space with: mkps -s64 -n -a rootvg
-s64 gives the number of physical disk partitions i.e. the size of the new paging space
And you have to know your LVM partition size for the volume group involved which you can find with lsvg rootvg (or whatever VG name you are going to use)

Hints with paging spaces.

• aim for 8 of them (a sensible number),
• all the same size (to even paging sapce I/O across them) and
• all on different disks (for performance)
• Mirror or RAID5 the paging space otherwise a paging space disk fault will halt your OS - it can't run as the paging space can be holding what will later go back to memory and having corrupt memory due to disk I/O problems is very unsafe.

Hope this helps, N
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Originally posted by: SystemAdmin

I must take issue with one thing there: I don't think that "8" is a reasonable number of paging spaces. The optimum number is one, just hd5, because obviously for best performance you don't want to be using any paging space at all: you want everything in real memory. Now that may not always be possible in the real world, but the appropriate number of paging spaces will vary from one system to another. If you're doing a lot of paging your performance is always going to be bad, and spreading the paging spaces across multiple disks isn't going to help all that much.
If it is necessary, then I would normally recommend fewer, larger paging spaces on dedicated disks. But I'd always try to reduce the amount of paging activity first, by VMM or application tuning.

From the original post, it's hard to know just what the problem is. More information might help us to provide a better answer.
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