How to get the mails if the OBIEE 11g services goes down.
Sorry but .... the mails of what?
Do you mean mails sent out by agents? Well .... if the service is down it sounds obvious there is nothing running able to send the mails ....
If you mean a notification mail telling you that the OBIEE service is down that's what any kind of monitoring tool does ... Of course again OBIEE can't really help you as .... it's down ....
Assuming you're talking about getting an email alerting you if OBIEE has gone down, here's some reading for you:
Automated Monitoring of OBIEE in the Enterprise - an overview
An introduction to monitoring OBIEE with Nagios
Advanced monitoring of OBIEE with Nagios
