A error problem with Oracle

Hello reader, I am a web support analyst working for Bentley Systems Inc. We have a many projects supported in PHP and are migrating slowly to a java-php abstracted applications. Most of our applications run with Oracle(8i) in the backend running on WinNT. We have a single RH (red Hat)6.2 server housing the SSL and nonSSL services for the customers. Offlate we have noticed that the oracle connections fails with "Warning _oci_open_server: ORA-12154 : TNS could not resolve service name in oci.inc.php " This entire applcation was running without any problem when the load or the request was less on the server. Offlate, with higher load, this message is being observed the most and we have no clue to resolve this issue. All of logons are with "OCIPLogon", I have even tried replacing this to "OCILogon". Doesnt solve any issue. Could anyone throw more insight to thies problem. Thanks Kaushik Kaushik Seetharaman Kumar Web Support Analyst, ITG Bentley Systems Inc. kaushik.kumar@bentley.com