Services and tnsnames in RAC environment

  Hi

we have 3 questions and would appreciate if anyone can answer these for us


1. we have created a service "ISF" on our RAC database

select * from dba_services

NAME      NETWORK    FAILOVER    FAILOVER  FAILOVER    FAILOVER     GOAL         ENABLED
                NAME          METHOD      TYPE           RETRIES      DELAY
============================================================================
SYS$BACKGROUND                                                                                   NONE           NO
SYS$USERS                                                                                               NONE           NO
isf             isf                                                                                               NONE           NO

when we created the ISF service, following entry was added to the tnsnames.ora file on both db nodes
ISF =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = db1-vip)(PORT = 1521))
    (ADDRESS = (PROTOCOL = TCP)(HOST = db2-vip)(PORT = 1521))
    (LOAD_BALANCE = yes)
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = isf)
      (FAILOVER_MODE =