How to calculate needed file-desc.

Hi Helpers! For applications using esql/c of informix with the SE-engine(V7.2) we need an idea how to calculate how many file-descreptors are needed. What is about the system overhead (UW2.1.3) and how are the differences in using *.so-libaries versus *.a-libs? Under SE every table has 2 files (*.dat/*.idx) so for every table there are a need of 2 descrs. But keep they alltimes open until the appl. is closed and what is used for locking? The default under UW213 of per proc filesdescr. is 64, the min is 20 and the max about 2000. This is a very with range. We got many problems with the default one(64) increased it to 128 worked until now. But yesterday i saw an EMERROR-signal. I will not only increase it again, i will try to calculate it as near as possible. Thank for any help Peter