How to start my test Application Server

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In oracle Application server ,I have two rac instances in oracle10g on solaris 10, we have 2 Instances one is testdb and other is production.

by some reason the instance of testdb is down ,now I need to restart the application server(test) Please guide me,how should I start it again.

it asks set environment variables ,I have xyz.env file how will I set this file and start it up

 

with kind Regards