oracle@lononl41:~> tnsping EUT01OP1

TNS Ping Utility for Linux: Version 10.2.0.4.0 - Production on 03-JUL-2009 05:54:17

Copyright (c) 1997,  2007, Oracle.  All rights reserved.

Used parameter files:

Used TNSNAMES adapter to resolve the alias

Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = lononl41-vip)(PORT = 1525)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = EUT01OP) (INSTANCE_NAME = EUT01OP1)))

OK (0 msec)

oracle@lononl41:~> sqlplus dbsnmp@EUT01OP1

SQL*Plus: Release 10.2.0.4.0 - Production on Fri Jul 3 05:54:25 2009
Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.

Enter password:

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production With the Partitioning, Real Application Clusters, OLAP, Data Mining and Real Application Testing options

SQL>

12505, 00000, "TNS:listener does not currently know of SID given in connect descriptor"
// *Cause:  The listener received a request to establish a connection to a
// database or other service. The connect descriptor received by the listener
// specified a SID for an instance (usually a database instance) that either
// has not yet dynamically registered with the listener or has not been
// statically configured for the listener. This may be a temporary condition
// such as after the listener has started, but before the database instance
// has registered with the listener.
// *Action: 
//  - Wait a moment and try to connect a second time.
//  - Check which instances are currently known by the listener by executing:
//    lsnrctl services <listener name>
//  - Check that the SID parameter in the connect descriptor specifies
//    an instance known by the listener.
//  - Check for an event in the listener.log file.