Srikanth,
Give Apache Lucene a try. Its open source and widely used search library.
You can index and search Tamil text as it does not suffer from unicode issues.
You can also create a RamDirectory Index, by reading the contents of
the CD into memory, if the data is not huge.
Else you can create a temporary directory on the client side to create
the persistent index and run your all search on that.
Best Regards,
Devjyoti