Muthahar,
A NullPointerException is so generic, that it's hard to track down or make any specific recommendations.
In order to further track the issue - I'd recommend investigating the following logs on each tier, to at least determine where the error is originating from. That will at least help you begin to narrow it down.
- Web
- $OTM_HOME/logs/glog.web.log
- $OTM_HOME/logs/tomcat/console.log
- App
- $OTM_HOME/logs/glog.exception.log
- $OTM_HOME/logs/glog.app.log
- $OTM_HOME/logs/weblogic/console.log
- $OTM_HOME/logs/oas/console.log
--Chris