Cause of OutOfMemoryErrors
http://confluence.atlassian.com/display/JIRA/Causes+of+OutOfMemoryErrors
Fix Out of Memory erros by Increasing Available Memory
http://confluence.atlassian.com/display/DOC/Fix+Out+of+Memory+errors+by+Increasing+Available+Memory
Managing Application Server Memory Settings
http://confluence.atlassian.com/display/DOC/Managing+Application+Server+Memory+Settings
Check the attachement also.
Attachments:
OutOfMemory.html (text/html)