udf - ressource temporarily unavailable
 

first of all, Merry Christmas

I am doing cfd analysis under Fluent 6.3 and in order to waste as less time as possible, I am holding different computation at the same time.
I tried to have 4 computations at the time, for all of them, I am using the exact same udf (I just change the value of some parameters in the script).
I could start the 1st 3 computations with no pb, but at the 4th one, I had the following message when compiling my udf:
cc -fpic -shared -ansi -Wall -O -DPTR_RESTRICT= -I/ap/Fluent.Inc/fluent6.3.2/bin/sh/: fork: Ressource temporarily unavailable
make[3]: *** [udf_names.o] Error 128
this is written 3 times with small differences, then:
make[3]: Target 'libudf.so' not remade because of errors.
make[3]: Leaving directory 'home/...'
make[2]: *** [lnia64] Error 2
make[2]: leaving directory 'home/...'
make[1]: *** [default] Error 2
make[1]: Leaving directory '/home/...'

I tried to compile the udf again by unlaoding it, or by deleting everything in the directory and copying a new library, udf scripts, and the case I want to study again, but the result remain the same.
If you have any ideas about why I am facing this issue, could you help me please?
Thank you very much.

As I thought, the problem seems to be due to the number of computation I can hold at the same time.
After ending the 3 other computations, I didn't receive any message of error for the fourth one.
But still, I would like to run 4 computations at the same time.
If you have any idea, could you tell me?