Hi Sanjeev,
Regarding to your issue, Iwould like to let you know there may not be enough heap size (virtual memory) allocated for the number of concurrent user sessions.
The HEAP size determine the initial amount of memory that is reserved after the QC service is started and the max size defines the maximum amount of memory that the QC service is allowed to allocate on the server. You can check these values by navigating to Help->About HP Application Lifecycle Management-> Additional information. There you can see the values defined for these parameters. If the initial value is set to equals the max value QC will reserve this amount of memory right of the start.
The other factor that could be responsible for larger amount of memory take is the number of users logged in QC and the exact tasks they are performing. These are the recommended values for the HEAP size depending on the number of users you have:
• Small: 128 - 256MB ~ Up to 10 concurrent user sessions
• Medium: 256 - 512MB ~ Up to 100 concurrent user sessions
• Large: 512 - 1024MB ~ Up to 250 concurrent user sessions
• Very Large: 1024 - 2048MB ~ Up to 350 concurrent user sessions
Please refer to the document below to have a better idea about it:
http://support.openview.hp.com/selfsolve/document/KM194705
I also inform you that there is no benchmark of heap size but it should be no more than 50% size of physical memory.
Please let me know if this information is helpful for you.