AIX Memory

Hi,

I am new to AIX , My manager asked to do a task,

Actually the memory the users are using are low but the system and cache memory is taking much memory . So, he wants to check me the system and cahe memory and he wants to reduce the or cleanup the system and cache memory . So please let me know how do that .
rishikirankAsked:
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woolmilkporcCommented:
Hi,
you can tell your manager that everything is OK.
AIX uses all its memory for filesystem caching instead of having it hang around uselessly.
wmp
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rishikirankAuthor Commented:
Hi woolmilkporc,

You are right but he doesn't want cahce to use the memory , he wants to decrease the amount of gb for cahce memory . Is there a way to decrease the cache memory .
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woolmilkporcCommented:
Yes it is, of course.

But I keep telling you that this will have counter-productive effects!
Why would you withhold AIX from doing something useful with its memory?

Anyway, the general tool used for tuning memory usage in AIX is called vmo ("virtual memory options").

The parameters which control filesystem cache usage are minperm%, maxclient% and maxperm%

You could lower them to let's say 15% and 20% (or even less, but that's really useful for very, very memory-hungry applications only, such as a big SAP instance).

Issue

vmo -o minperm%=15vmo -o maxclient%=20vmo -o maxperm%=20

Add -p to the options (vmo -p -o ...) to make the changes permanent across reboots.

The immediate effect will most probably not be as big as expected, you will have to wait some time, because AIX is a bit conservative in its memory management.

You can force it to do immediately what you want, by issuing

vmo -o strict_maxperm=1
 
But please be very careful with this last option! AIX will obey and throw away most of its filesystem cache, regardless of whether it is needed at that very moment or not!

To learn a bit about vmo and its options you can issue

man vmo
or
vmo -L
or
vmo -h [tunable_parameter]


Replace [tunable_parameter] with the name of the parameter you'd like to get information about.

A good source for learning:

http://publib.boulder.ibm.com/infocenter/aix/v6r1/topic/com.ibm.aix.prftungd/doc/prftungd/perf_ovw_vmm.htm

Good luck!

wmp

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rishikirankAuthor Commented:
it helped me partially
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