Enabling Memory page sharing to active in RHEV3.0 managing RHEV Hypervisor 6.2

Hi,

I have installed RHEV Hypervisor 6.2 and i am managing it with RHEV manager 3.0. when i checked general tab of the host in RHEV manager, i see memory page sharing is shown as inactive.

can anyone help me to understand why it is inactive??? and how to make it active.

Thanks,

Inbaraj