This is a client side error.
Nothing to do with the database. Usually, if the hostname used in tnsnames.ora are not resolvable by the client
then the subject lined error appears.
For my case, I was facing this
error for a 2 node RAC cluster 11gR2 database. We are using SCAN address in the
tnsnames.ora. Even though the client can resolve scan still it's failing.
Why?
Because, not only the SCAN but
all server in the cluster needs to be resolvable by application clients. This includes the host VIPs and
real IP of all the servers in the RAC configuration.
Look at the demonstration of this
error:
I can ping the DB alias from
client pc.
#tnsping DB1
TNS Ping Utility for
Linux: Version 11.2.0.1.0 - Production on 31-JAN-2013 14:13:09
Copyright (c) 1997, 2009,
Oracle. All rights reserved.
Used parameter files:
/opt/oracle/product/11.2.0/client_1/network/admin/sqlnet.ora
Used TNSNAMES adapter to
resolve the alias
Attempting to contact
(DESCRIPTION = (ADDRESS=(PROTOCOL=TCP)(HOST=db1-scan)(PORT=1521)) (CONNECT_DATA
= (SERVER=dedicated) (SERVICE_NAME= db1.mycompany.com)))
OK (0 msec)
But, Can't connect to the
database using SQLPLUS.
sqlplus ***/****@db1
SQL*Plus: Release
11.2.0.1.0 Production on Thu Jan 31 14:13:35 2013
Copyright (c) 1982, 2009,
Oracle. All rights reserved.
ERROR:
ORA-12502: TNS:listener received no CONNECT_DATA from client
It's because, the
client firewall rule is blocking it from communicating either.
VIP/Real IPS of all
the servers associated with RAC configuration.
The problem was fixed
after fixing firewall in accessing VIP.
