[CentOS] How to Increase Swap Memory in Centos 4.4?

Stephen Harris lists at spuddy.org
Tue Apr 3 15:41:54 UTC 2007

On Tue, Apr 03, 2007 at 11:20:41PM +0800, John Summerfield wrote:
> Bart Schaefer wrote:
> >On 4/3/07, Pham Hai <haisoncompany at gmail.com> wrote:
> >>To install Oracle Database 10g, I need to increase the swap memory to 
> >>1004
> >>MB.
> >
> >Tangential aside:  Does anyone have an informed opinion on whether the
> >"swap should be double RAM" rule still makes sense?
> It never did. I couldn't see why, if I upgraded my Pentium from 64 

It used to make sense on older BSD systems (eg SunOS 4) because of how
the virtual memory paging system worked.  If you had 'n' Mb of RAM then
the first 'n' Mb of swap was used to "shadow" RAM somehow (I'm hazy on the
details) and so if you had '2n' of swap then you only had '2n' of virtual
memory, not the '3n' you'd expect.  Linux never did this and I believe
newer BSDs don't either.  The "swap=2*RAM" never made sense for Linux.

> Mbytes+128 Mbytes I should add swap if I added 128 Mbytes RAM.

Under the older BSDs adding memory without increasing swap didn't result
in larger VM sizes because of the above description.  Fun, huh? :-)



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