Swap Space Problems

[Alan's Home for Wayward Notes File.]

In article <1623 at opus.NMSU.Edu>, bemery at nmsu.edu (Bryan Emery) writes:
> 
> The installation guide suggested that I need about 2-3 times the amount of
> virtual memory in swap space and that two swap areas is more efficient than
> one.  So, I took 16*3=48 Mbytes, divided that by two and set up two 24 Mbyte
> partitions for swapping.

	The suggestion of 2-3 time physical memory is probably good
	for most typical application loads.  There is no way the
	installation guide can predict that you might have an application
	that uses 500 MB (to pick a truly random number) of virtual memory.
	Remember this point.
> 
> Now, I am getting lots and lots of memory problems.  For example, when someone
> is using SAS on the console in windows, no one else can even login.

	"Typical".  Why do I suspect SAS may not be typical...  So
	if you have a spare partition the right size, add more page/
	swap space.  Multiple spindles are good if you actually start
	doing pageing I/O.  If you have access to a shell while SAS 
	is running use pstat(8) and ps(1) to look at page/swap space
	and virtual memory usage.  If either exit with a message that
	resembles "out of core", then you're definately out of page
	and swap space.

> 
> [ Description of a problem with su(1) ].

	This is more likely a permission problem, so look there first
	to make sure.
> 
> I assume these problems are related to not enough available memory which
> translates to not enough swap space.

	The SAS problem almost certainly is.
> 
> But, I thought (according to the guide) I had plenty.
> 
> Any suggestions?  Please respond by e-mail.  Thanks!!

	I'll reply and post both, since it may be of general
	interest.
> 
> Bryan Emery
-- 
Alan Rollow				alan at nabeth.cxn.dec.com