Add more listeners and load balance

See TNSnames configuration, Listeners

Initial configuration of tnsnames.ora

SRV_PRO =
  (DESCRIPTION =
    (ADDRESS_LIST =
#      (ADDRESS = 
(PROTOCOL = TCP)(HOST = 10.31.129.27)(PORT = 1525))
      (ADDRESS = 
(PROTOCOL = TCP)(HOST = db001srv)(PORT = 1525))
    )
    (CONNECT_DATA 
=
      (SERVICE_NAME = SRV_PRO)
    )
  )

Initial configuration of listener.ora

LSNR_SRV_PRO =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 
db001srv)(PORT = 1525))
  )
SID_LIST_LSNR_SRV_PRO =
  (SID_LIST 
=
    (SID_DESC =
      (GLOBAL_DBNAME = SRV_PRO)
      (ORACLE_HOME = 
/app/oracle/product/9.2.0)
      (SID_NAME = SRV_PRO)
    )
  )

Final configuration of tnsnames.ora

SRV_PRO =
(DESCRIPTION =
(LOAD_BALANCE=yes) 
# (ADDRESS = (PROTOCOL = TCP)(HOST = 10.31.129.27)(PORT = 1525))
(ADDRESS = (PROTOCOL = TCP)(HOST = db001srv)(PORT = 1525))
(ADDRESS = (PROTOCOL = TCP)(HOST = db001srv)(PORT = 1526))
(ADDRESS = (PROTOCOL = TCP)(HOST = db001srv)(PORT = 1527))
(CONNECT_DATA =
(SERVICE_NAME = SRV_PRO)
)
)

Final configuration of listener.ora

LSNR_SRV_PRO =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = db001srv)(PORT = 1525))
)
SID_LIST_LSNR_SRV_PRO =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = SRV_PRO)
(ORACLE_HOME = /app/oracle/product/9.2.0)
(SID_NAME = SRV_PRO)
)
)

LSNR_SRV_PRO_LB1 =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = db001srv)(PORT = 1526))
)
SID_LIST_LSNR_SRV_PRO =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = SRV_PRO)
(ORACLE_HOME = /app/oracle/product/9.2.0)
(SID_NAME = SRV_PRO)
)
)

LSNR_SRV_PRO_LB2 =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = db001srv)(PORT = 1527))
)
SID_LIST_LSNR_SRV_PRO =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = SRV_PRO)
(ORACLE_HOME = /app/oracle/product/9.2.0)
(SID_NAME = SRV_PRO)
)
)