How can I increase limit on datasize under Ultrix3.1?

[Baiju Patel]

I am running this program (VLSI placement and routing prog) which requires
lot of memory. Unfortunatly, for some strange reasons, I am not able to 
increase the limit on datasize. Which makes my program to abort when 
the memory requirement exceed 21M. I trying increasing limit by 
typing 
limit 30m
I get a message saying
limit: Not owner

If I try the same command as root, it accepts it. Except, limit remains
unchanged. I tried this command on microvax GPX II, VAX 11/780, VAX 8800
and so on. It does not seem to work anywhere. 

Am I doing something wrong or is it system limitation?

Please send reply directly to patel at ecs.umass.edu

Thanks in advance

baiju