Use diff alias names ( TNS Name ).

Code:
1)
ACC1.World =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = IP1)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = ACC)
)
)

2)
ACC2.World =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = IP2)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = ACC)
)
)
Abhay.