unexpected lock with stored procedures

I'm working with an Informix 7.12 UC1 on a HP9000 E45 HPUX 9.04 system. I have several parallels processes which execute stored procedures with insert,update and select orders on the sames informix tables. Because in such cases, "record locked" problems are still normal, I resolve them with the "SET LOCK MODE TO WAIT x(seconds);" instruction which allow the currents processes to wait x seconds before redo the instruction or return an error code. For the SELECT case, the "SET ISOLATION MODE TO DIRTY READ" allow the process and the stored procedure to return data even if the record is locked. But sometime, the stored procedure is stopped by a dead lock statement ( or something like that, because the table is entierely locked) without any SQLERROR Code Or ISAM CODE an the Unix process must be handly killed !!! I haven't no more ideas about a solution. If you can, help me at Francis.Guilhin@toulouse.tecsi.com Thanks .