Try something like this:
Code:
ORCL=
  (DESCRIPTION=
    (ADDRESS=(PROTOCOL=TCP)(HOST=PrimaryServer)(PORT=1521))
    (ADDRESS=(PROTOCOL=TCP)(HOST=StandbyServer)(PORT=1521))
    (LOAD_BALANCE=yes)
    (FAILOVER_MODE=(TYPE=SELECT)(METHOD=BASIC)(RETRIES=5)(DELAY=1))
    (CONNECT_DATA=(SERVER=DEDICATED)
    (SERVICE_NAME=ORCL.WORLD))
  )