Informix returns SQLCODE=-439

Hello, after a two month of perfect working, our web build on Informix + Apache with PHP started to return an SQLCODE=-439 as a result of ifx_connect. The error is returned only sometimes usually when the traffic on the server increase (the total traffic is some 1000 visits a day). Configuration: OS Solaris 2.6 Informix IDS 7.30 Apache 1.3.9 with PHP 3.0.11 as a module This is a quite unexpected error as this should occures only within an incorrect function call in INFORMIX-ESQL/C. I dont know whether this error comes from a poorly tuned Informix (the onconfig file) or it is a bug in php-informix connection? Thank you for any idea. Mark