what are the remedies available when your swap space is reported as being full?

this hasnt happened to me, but i'm just curious to know...

Incidentally, what is the origin of this rule that i keep hearing -

swap space = 2 * RAM

I've heard this kind of rule being recommended when you're running SAP, but for home systems??????? especially when most home PC's are touching 256/512MB.....

regards,

kishor