X dies - out of swap space

[David Banning]

Apr 10 13:41:39 skytrackercanada /kernel: swap_pager_getswapspace: failed
Apr 10 13:42:29 skytrackercanada last message repeated 79 times
Apr 10 13:42:29 skytrackercanada last message repeated 16 times
Apr 10 13:42:29 skytrackercanada /kernel: pid 355 (XFree86), uid 0, was killed:
 out of swap space

All of a sudden, every few days, under no great load, X dies and I lose
my keyboard. The rest of the machine runs fine. It is still serving 
web pages and I can telnet in, but I cannot control the console.
A "ps ax" shows that indeed X is not running.

I have searched the list for previous answers but I would like to find
out why it is happening.

The best suggestion I heard was to set datasize to 128M in
.initrc or .xsession. BTW, where is the man page for those files?

Any suggestion or info on the above subject would be helpful.