1)For <11gR2, Is it possible to use netca/netmgr to add fail_over/load_balance parameters in client and servers network files?. Manually adding these parameters to tnsnames.ora/listener.ora sometimes cause problem due to space/syntax issue.
2)For 11gR2 I guess these special parameters not needed since SCAN automatically takes care of this. Am I correct?
1) I have not tested it but it should be possible to use netmgr at least with 11.1: see http://docs.oracle.com/cd/B28359_01/network.111/b28316/advcfg.htm#i465213.
2) This depends on Oracle Client version that is used: see pages 4 and 5 in http://www.oracle.com/technetwork/database/clustering/overview/scan-129069.pdf.