1st of all, do a df -k /tmp to see how big is your swap space.



2) Go get some big ascii file. E.g. /var/adm/messages
E.g.
cd /var/adm
cat mess* > my_msg
cat my_msg my_msg my_msg my_msg > my_msg.1

You can write a quick while loop to do the above until my_msg.1 becomes slightly smaller than the swap space.

3) mv my_msg.1 /tmp

The reason is to deny the OS from using swap space when your memory runs out.

4) Write a simple perl code that slurps the /tmp/my_msg.1.
E.g
while read <MY_FILE>

You will definitely runs out of memory.
If this is not desired, play around with the size of my_msg.1 until it is the size of the intended memory consumption.

you can use this command to see how much physical memory you have:
prtconf | grep -i mem