Ack bad idea. Hes running on solaris and /tmp is a virt filesystem that dumps to ram/swap switching one evil (disk i/o) for another (memory starvation -- swap out) is not a great idea. As noted in one of his replys above his cpu is near 100% durring the run so it looks like CPU contention.

If he can, it's better to use pipes to decompress the file right into the program that will read it. That way you get the best of both worlds. But I doubt that putting the decompressed file on /tmp is a bad idea. That's exactly the kind of file you do want to put on /tmp. It will be used once right after it's created, then destroyed. What else is /tmp for? The fact that Solaris caches it aggressively is good, not bad.

The key point, however, is:

VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV
        DO NOT DECOMPRESS THE FILE IN PLACE.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

If you decompress the file in place, you have to recompress it. That wastes over half of your CPU time.