As per your suggestion , i deleted the lock file and i am able to start the alfresco service.
Issue is that - I am facing this particular problem for every 3 - 5 days.
And i never shutdown my server nor stopped alfresco. What might be the cause ? & How to Overcome this permanently ?
Kindly help me - its in production. ERROR IS : Service Temporarily Unavailable The server is termporarily unable to service your request due to maintenance downtime or capacity problems Please try again later