The topic is described in Doc ID 453293.1

http://www.programering.com/a/MjNxgTNwATU.html

tnsnames.ora record examples:

Client Side Load Balancing

Following is an example of TNS net service alias for client side load balancing
CLIENT_LOADBALANCE=
 (DESCRIPTION =
  (LOAD_BALANCE = yes)
  (ADDRESS = (PROTOCOL = TCP)(HOST = node1-vip.idc.oracle.com)(PORT = 1521))
  (ADDRESS = (PROTOCOL = TCP)(HOST = node2-vip.idc.oracle.com)(PORT = 1521))  
  (CONNECT_DATA =  
   (SERVICE_NAME = service.idc.oracle.com)  
  )
 )

Connect Time Failover

Sample connect time failover TNS net service alias address_list defaults the failover=on

CLIENT_FAILOVER=
(DESCRIPTION =  
 (ADDRESS_LIST =  
  (ADDRESS = (PROTOCOL = TCP)(HOST = node1-vip.idc.oracle.com)(PORT = 1521))
  (ADDRESS = (PROTOCOL = TCP)(HOST = node2-vip.idc.oracle.com)(PORT = 1521))  
 )
 (CONNECT_DATA =
   (SERVICE_NAME = service.idc.oracle.com)
 )
)

Client Side Load Balance & Connect-time Failover Connect String

CLIENT_LOAD_FAILOVER=
(DESCRIPTION =
 (ADDRESS_LIST =
  (LOAD_BALANCE = yes)
  (ADDRESS = (PROTOCOL = TCP)(HOST = node1-vip.idc.oracle.com)(PORT = 1521))
  (ADDRESS = (PROTOCOL = TCP)(HOST = node2-vip.idc.oracle.com)(PORT = 1521))
 )
 (CONNECT_DATA =
  (SERVICE_NAME = service.idc.oracle.com)
 )
)

TAF - Client Side Configuration

Failover Mode Type can be Either SESSION or SELECT. Session failover will have just the session to failed over to the next available node.The select query will not be resumed.
Simple TAF can be configured on the client side tnsnames.ora with following entry: