Can anyone please let me know that what are Xen Hypervisor 4.x limitations. How many virtual machines i can create with what memory and cpu?
I think according to the docs the limits are a little higher with OracleVM than on "plain" Xen, but this is best checked in the Xen wiki.
Highest I've tested was around 200 domUs iirc, there was no problem. Note you might have to tune the xen heap size for more, there's a tech doc about it at Citrix' Website.