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Home -> Community -> Usenet -> c.d.o.server -> Re: Free memory in Solaris
thiru wrote:
>
> Hi Bass,
> You are absolutely right. I too got tired of finding an easy way to
> find out Free memory on Solaris. vmstat or sar does not tell you this.
> Looks like Solaris Uses up almost every byte of Physical memory you
> add on, without actaully consuming it.
>
> However you can track Page Faults/sec( pi,po,fr) columns in Vmstat to
> determine if your system is Paging excessively and wants more Physical
> memory. If 'fr' (pages freed) steadily declines then the System needs
> more memory ,if I am right.
>
> Also Swapping should be Zero.
>
> Hope this helps U , a little bit.
> -Thiru
>
>
> Bass Chorng wrote:
>
> I am trying to find out how much physical memory is left
> after I size my SGA in Solaris. This should be a very
> basic and simple question. But it almost turns into a
> nightmare.
>
> I know the answer is NOT vmstat - if thats what you are
> thinking. It is NOT that simple with Solaris. It IS that
> simple with HP-UX, that vmstat shows free lists of memory.
> You can multiple your free lists by 4K and get the free
> memory in bytes.
>
> I have checked various webs, even with Sun support. There
> simply has no straight answers. Basically you need 3rd party
>
> tools. ( I have no idea what vmstat tells you then, to be
> honest ).
> I know man page with vmstat is either wrong or misleading.
> I says the column free tells you free mem in bytes, then
> a book I read says it tells you free mem in pages - but
> neither one matches reality. They are both way off.
>
> Then I read a white paper on Sun Support, it says, it is not
>
> easy....etc, and it never gives you a clear answer.
> I can hardly believe this.
>
> So, there must be trillions of DBAs out there sizing
> memories
> in Solaris everyday. How do you guys detemine how much free
> ( physical ) memory is left on a system? Don't you size
> stuff like sort_area_size AFTER knowing how much you have
> free ?
>
> I hope I am completely wrong, because this question seems to
>
> be too simple and easy to be answerless. So I am seeking
> help
> from the largest pool of Oracle expertises out there -
> please
> share your experience if you know how. I would certainly
> appreciate your help.
>
> -Bass Chorng
> DBA
> Lucent Technologies.
To quote an Oracle friend of mine:
"Memory doesn't last longer if you don't use it"
Solaris uses up all available memory so that the server runs basically as a continuous cache...
(Vaguely speaking) if sizing your SGA leaves 50% of the RAM free - then Solaris will allow everything else (buffers for files, processes etc) to use up all of that...why wouldn't it ?
A very good book is Adrian Moorcrofts Solaris Performance Tuning. It describes how memory (plus a whole lot of other things) is handled under Solaris and how to use vmstat, sar etc to decide if you need more memory.
HTH
--
"Some days you're the pigeon, and some days you're the statue." Received on Mon Jun 21 1999 - 09:30:40 CDT
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