Database Software

hi all ,

i have oracle 11g .2 with rac and asm in linux 5
i have 2 nodes

can you please advice in my question below :

i read of SCAN which is provide single name for client to access the database and tnsnames for client
will be not change if you add or remove other node and we have 2 option to define the scan
1.DNS. 2.GNS
the first one is by ask the netwrok admin to create name to resolve 3 ips,and the second on when you have dhcp
and we have another option is be define only one ip in hosts file for each node , i think this is what i have due the below ,the command below must be retain 3 ips

[oracle@ccbs01 admin]$ nslookup ccbs-scan
;; connection timed out; no servers could be reached

vi /etc/hosts
# SCAN
x.x.x.120 ccbs-scan.localdomain ccbs-scan and this line is define in 2 node (2 server one ccbs01,ccbs02)

my question is when we have client with same version 11.2
connect to db and one node is unavailable is it switch to another node due to the tnsnames include scan ip
x =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = x.x.x.120)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = x.domain)
)
)

cuz i read the scan do the load balancing and failover???


one more think

ccbs01

have vip x.x.x.115

ccbs02
have vip x.x.x.116

when i turm off the ccbs 01

in ccbs 02

ifconfig -a
return 115 and 116
means the vip switch to another node????


last question please

when we have database 11g.2 rac but the client is older
the advantage of scan will be loss till add the below

x =(DESCRIPTION= (CONNECT_TIMEOUT=10)(RETRY_COUNT=3)
(ADDRESS_LIST= (LOAD_BALANCE=on)(FAILOVER=ON)
(ADDRESS=(PROTOCOL=tcp)(HOST= x.x.x.115)(PORT=1521))
(ADDRESS=(PROTOCOL=tcp)(HOST= x.x.x.116)(PORT=1521))
(CONNECT_DATA=(SERVICE_NAME= x.domain)))

115,116 vip for 2 node

but the error appear ora-12154 ????

i want to use the above tnsnsames in other client and use 2 parameter to switch to another address without delay the user if first ip is corrupted???

advice please