multi thread - Informix

Dear All, We have a multi thread C++ program. The threads fetch data (with prepared cursor) from an Informix DB parallel, but we got coredump (not always) The operating system is: ReliantUNIX-Y 5.45 B2005 RM600 4/768 R4000. We uses the following packages: PKGINST: SIthreads NAME: Threads and Reentrant System Libraries CATEGORY: optional ARCH: R4000 VERSION: 5.45B20 LOAD: 04 BASEDIR: /opt VENDOR: Fujitsu Siemens Computers PSTAMP: senior020430112053 INSTDATE: Jan 28 2004 02:29 PM STATUS: completely installed FILES: 288 installed pathnames 1 partially installed pathnames 19 shared pathnames 30 directories 4 executables 17976 blocks used (approx) PKGINST: ICD230C1 NAME: INFORMIX-CLIENTSDK CATEGORY: application.database ARCH: R4400 VERSION: V2.30.UC1 PSTAMP: dagobert990604222446 INSTDATE: Jan 28 2004 12:21 PM STATUS: completely installed FILES: 997 installed pathnames 44 linked files 64 directories 43 executables 103681 blocks used (approx) Probably something is not thread safe, or we using something wrongly . But we don't know where is the problem. What is the most important things in case develope a mult thread program which use Informix DB? Have you got an example? Thank you in advance Tamas Schummel