All, I have a 2 node 10g RAC setup on linux boxes with NetApp storage. It is a shared infrastructure where different applications are accessing the database so I have created one service per application. One cluster node is configured as preferred and the other as available for the services. Applications are using client side load balancing using LOAD_BALANCE=ON in their tnsnames.ora and receiving ORA-12545 occasionally. I enabled the debug trace for listener and found that users are getting this error only when their database connection requests are being received by the listener running on the available node (Please note that the service user is intending to connect is not running on available node). If I modify the service and made both cluster node preferred then end users does not get any error. To explain this further, consider the extract from a client's tnsnames.ora as shown below: (For security I have renamed the hostnames) ORCL.S001 = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = host01-vip.domain.com)(PORT = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST = host02-vip.domain.com)(PORT = 1521)) (LOAD_BALANCE = ON) (FAILOVER = ON) ) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = S001.domain.com) ) ) Client is trying to connect to the database ORCL using Oracle 10g Service "S001.domain.com". But when client connects to the database ORCL, occasionally receive error ORA-12545. To analyze further, I enabled the debug trace in the sqlnet.ora at client machine by setting parameter TRACE_CLIENT_LEVEL = support and connected the database ORCL using the "S001.domain.com" service. Again I received ORA-12545 and found following in the sqlnet.log on client machine: Fatal NI connect error 12545, connecting to: (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=host02-vip.domain.com)(PORT=1521))(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=S001.domain.com)(CID=(PROGRAM=C:\oraclexe\app\oracle\product\10.2.0\server\bin\sqlplus.exe)(HOST=PDUBAR-AU)(USER=pdubar)))) VERSION INFORMATION: TNS for 32-bit Windows: Version 10.2.0.1.0 - Production Windows NT TCP/IP NT Protocol Adapter for 32-bit Windows: Version 10.2.0.1.0 - Production Time: 13-MAY-2008 11:27:34 Tracing to file: C:\Documents and Settings\pdubar\cli_5308_1.trc Tns error struct: ns main err code: 12545 TNS-12545: Connect failed because target host or object does not exist ns secondary err code: 12560 nt main err code: 515 TNS-00515: Connect failed because target host or object does not exist nt secondary err code: 1001 nt OS err code: 0 So from the trace file, it clearly shows that client is receiving error ORA-12545 only if it is connecting to "S001.domain.com" on node host02-vip.domain.com. But why client is not able to connect to S001.domain.com service on host02-vip. Should not listener running on host02 redirect the connection to host01?. Here is the output of lsnrctl services from host02: Service "S001.domain.com" has 1 instance(s). Instance "ORCL1", status READY, has 1 handler(s) for this service... Handler(s): "DEDICATED" established:7 refused:0 state:ready REMOTE SERVER (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=host01-vip)(PORT=1521))) Remote_listener parameter is also set on this cluster database. My question is : Is this the expected behavior? If yes then what is fun of enabling the load balancing? Thanks & Regards -Harish Kalra --------------------------------- Has your work life balance shifted? Find out.