>How to avoid index file corrupt ??

Rebuilding an index on Init() is not a good solution. It is overkill and slow (what if you have many tags in a big table with lots of records)?

The answer is a UPS in every workstation and at the server. Good quality LAN hardware (NICs, cabling, etc.)

Good training to the users, to properly close files and logout before going home.
And periodic maintenance (index rebuilding) doesn't hurt either.

I follow these precepts and rarely have an index problem.