If you are wondering why your jdbc thin client connections to an Oracle Real Application Cluster instance are failing to connect, one possible reason is that you may not be using the correct connection syntax. An Oracle RAC instance can be identified by running tnsping and looking at the host list and the FAILOVER setting:
/cygdrive/h>tnsping MYDBTNS Ping Utility for 32-bit Windows: Version 10.2.0.1.0 - Production on 08-JUL-2008 17:02:15
Copyright (c) 1997, 2005, Oracle. All rights reserved.
Used parameter files:
c:\lib\oracle-10.2\network\admin\sqlnet.oraUsed LDAP adapter to resolve the alias
Attempting to contact (DESCRIPTION = (SDU = 8192) (TDU = 8192) (ADDRESS_LIST = (ADDRESS = PROTOCOL = TCP)(HOST = host1)(PORT = 1621))(ADDRESS = (PROTOCOL = TCP)(HOST = host2)(PORT = 1621)) (LOAD_BALANCE = on) (FAILOVER = on ) ) (CONNECT_DATA = (SERVICE_NAME = MYDB) (FAILOVER_MODE = (TYPE = session) (METHOD = basic) (RETRIES = 20) (DELAY = 5) ) ) ) OK (0 msec)
The standard JDBC thin URL syntax doesnt seem to work correctly here:
jdbc:oracle:thin:@host1:1621:MYDB
Seems to fail (at least for me), but the alternative unwieldy syntax:
jdbc:oracle:thin:@(DESCRIPTION=(LOAD_BALANCE=on)(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=host1)(PORT=1621))(ADDRESS=(PROTOCOL=TCP)(HOST=host2)(PORT=1621)))(CONNECT_DATA=(SERVICE_NAME=MYDB)))
Works fine.