hi
u have to configure your tnsnames.ora file setup for using transparent application failover.(runtime failover)
check with this
ORCL =
(DESCRIPTION=
(FAILOVER=ON)
(ADDRESS_LIST =
(ADDRESS=(PROTOCOL=TCP)(HOST=PROD1)(PORT=portno)
(ADDRESS=(PROTOCOL=TCP)(HOST=PROD2)(PORT=portno)
)
(CONNECT_DATA=(SERVICE_NAME=PROD)(SERVER=shared or dedicated)
(FAILOVER_MODE=(TYPE=select)(METHOD=basic))
)
)