we are using db2 v8.2.2 (FP10) and aix 5.2
in production box we created two instances db2vc1 for client and db2vi1 for serever, is it necessary in db2 v8 or is it mandatory?.

Thank you in advance for your help.

Its not mandatory. Its upto you how you setup your box for Db2.

the server instance includes a client
only if you want to handle db2 local or remote - independent from the server instance, you would create a client instance..