PerGem heap error in Tomcat 7 - Plane DA 7.1 and WebTop 6.8 deployed in Tomcat 7,OS Windows Server 2

DeepakEMC

Dear Experts,

We have CS 7.1 environment,with a Tomcat 7 Application Server deployed with da7.1,Webtop6.8 in OS -Windows Server 2012 R2 Standard(VM).Few days back OS of Application Server got crashed and we could not able to rebuild it as it was in past.
New VM with same configuration is provided to us with OS - Windows Server 2012 R2 DataCenter and in this system we have reconfigured same version of Tomcat7 and deployed same DA 7.1 and Webtop6.8 and it works fine.But after an hour Tomcat don't respond.In logs we get PerGem heap error and once we restart it again works fine.

Could any one let me know what could be the issue and what need to be done.

Regards,
Deepak Dash(TCS)