yes it is, you can see it in the avamar oracle documentation to see how to configure it...
basically you install the avamar client and the rman agent, and then configure the avamar oracle rac....
But in the guide, it says
Support for Oracle RAC.
Avamar for Oracle Client supports backups andrestores of an active/active Real Application Clusters (RAC) configuration forOracle versions 10gR2 and 11g R2 on the following platforms:
•IBM AIX 6.1, 64-bit
•Red Hat Enterprise Linux 5, 64-bit
•Solaris 10, 64-bi