In reply to Kat.

You've done all the right things. 180 million observations is not huge by modern standards, so you might be running out of space in WORK. Your SAS administrator might be able to help you allocate more space for the WORK directory. Or you can use a permanent libref, but remember to delete those files when you are finished!

Your idea to break up the problem into smaller ones is quite reasonable. That is one of the tips I give for running huge simulations in Chapter 6 of Simulating Data with SAS (particularly section 6.4.5).