Problems with optimization

[cbas25 at vaxa.strath.ac.uk]

I have been trying to compile a rather large (Fortran) program
using the -O3 directive to do all optimizations.  Under these
conditions the compilation fails with the error message:-

usplit: Error: cannot read/write ucodes from/to /tmp/ctmlua01046//
               tmp/ctmsa01046: Error 0

(the message appears all on one line), together with the message:-

                       dks0dls0 out of space.

When compiled without optimization there are no errors, and the 
compiled program works normally.
I am running this on a Personal Iris 4D20 with 12Mbytes of memory
and the usual 380 Mbyte disk.  On the disk the /dev/root filesystem
has 10663 blocks available (out of 31050), and the /dev/usr filesystem 
has 45401 blocks available (out of 482816), but I can probably get the
percent usage down to about 87% quite easily.  The total size of the
ucode files (*.u) is 4768829 bytes, of which the largest file has
978588 bytes. (Each file consists of several smaller routines, and I
would prefer not to have to split them up). When compiled without
optimization the final exectuable file amounts to 1750460 bytes.

Can anybody help??      What am I doing wrong??   Any advice will
be much appreciated.

Thanks
Peter Bladon