Hi Praveen,
>> Can we apply the archieve log files which are taken from the oracle 9i server on the other oracle 10 g r2 server.
Let's think about it. Oracle 9i is not aware of the 10g formet, because 10g did not exist when 9i was written.
Hence, backwards compatibility is always maintained, buit forward compatibility is always risky.
In your case, the whole point of DataGuard is to have failover, and it does not make sense not to have the exact same releases levels on both servers.
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>> I am very new to the database administration side.
If you need to get started fast, get the "Oracle Data Guard" book:
http://www.rampant-books.com/book_2004_2_dataguard.htm