I've 2 11gR2 DBs with versions 18.104.22.168 and 22.214.171.124. I've a requirement to keep both these DBs in sync for HA. I am thinking of using Oracle Data Guard (DG) between these 2 DBs to keep them in sync.
I read that to setup DG, both primary and standby have to be off same Oracle Major Version. Hence, I thought DG can be implemented between 126.96.36.199 and 188.8.131.52 as the Major version remains 11gR2.
Please note, both these DBs are hosted 2 different OS env. One is on Aix 5.3 and another one is on Suse Linux.
This will depend upon type of Standby.
For Logical is is possible, for Physical no.
Here's a supporting MOS document :
Mixed Oracle Version support with Data Guard Redo Transport Services [ID 785347.1]