Hey maleksalim_2,
The analog endpoints on the VG224 register as sccp and therefore should behave the same as sccp IP phones.
Here's a doc that talks about the failover architecture on the UCM for sccp. I think this is what you are looking for?
https://supportforums.cisco.com/document/74666/cucm-ip-phone-sccp-keepalive-and-failover-architecture
Thanks
Sree