Hi All, I got ' ORA-12535: TNS:operation timed out' error while trying to connect to a database from my client machine via SQLPLUS. Database machine and my client machine are under different domains. The database port is already open to my client machine, tnsping works fine. The sqlplus connection to the database works fine on other client machines which under same domain as the db machine. And also sqlplus connections from my client machine to other databases work fine. Please help me on this issue. The following is the output on my client machine: H:\>sqlplus SQL*Plus: Release 9.2.0.6.0 - Production on Tue Mar 10 11:32:11 2009 Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved. Enter user-name: system@ocval Enter password: ERROR: ORA-12535: TNS:operation timed out H:\>tnsping ocval TNS Ping Utility for 32-bit Windows: Version 9.2.0.6.0 - Production on 10-MAR-2009 11:24:27 Copyright (c) 1997 Oracle Corporation. All rights reserved. Used parameter files: C:\oracle\ora92\network\admin\sqlnet.ora Used TNSNAMES adapter to resolve the alias Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = ocdbval.vali dated.mbl)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = ocval.validated.mbl))) OK (20 msec) Thanks, Lu