16039, 00000, "RFS request version mismatch"
// *Cause: A request to archive a redo log to a redo transport destination
// failed because of an Oracle software version mismatch at the
// *Action: Verify that a compatible version of Oracle software is running at
// the redo transport destination.
Thanks, How do I verify if 220.127.116.11 and 18.104.22.168 are compatible with each other? The compatibe parameter b/w databases is same.
They aren't. The compatible parameter has nothing whatsoever to do with anything in this case (although they do need to be the same for physical standbys - that's not the cause of the issue you have).
The documentation (Getting Started with Data Guard) says:
The same release of Oracle Database Enterprise Edition must be installed on the primary database and all standby databases, except during rolling database upgrades using logical standby databases.
I have my primary running on 22.214.171.124 and standby on 126.96.36.199. However, "compatible" is set to "188.8.131.52" in both databases.
Ouch! Why would you have your standby on a different version?!?! Your standby database is a safety net in case your primary is unavailable. By keeping it at a lower version, you have removed that safety net. This should be rectified before a disaster strikes and you need the standby.
The COMPATIBLE parameter doesn't matter here. You are generating redo on an 11.2 database and trying to apply that redo to an 11.1 database. It won't work.
Before the upgrade of the primary did you read the Oracle documentation on how to upgrade when you have a standby? Here is a link to that section of the documentation:
At this point, I would instance the primary's version on the standby server. I would then recreate the standby from a backup of the primary. Then everything should work just fine.
You did not finish this "Primary was upgraded to 184.108.40.206 a few weeks back."
You should have upgraded the Standby as part of the Primary upgrade.
Overview of how to do it in the future
Disable log shipping from the Primary
Install 220.127.116.11 on Standby
Startup Standby in recovery mode
Install 18.104.22.168 on Primary
Run upgrade SQL on Primary
Re-enable log shipping
Monitor the redo apply from Primary to Standby --- this will also upgrade the Standby data dictionary
One thing you can try is to roll forward the standby with an RMAN incremental backup. See Note 836986.1 for complete steps.
Otherwise, you can follow the steps used to create a physical standby as documented here:
But you won't need all of the steps because most are already done. You will need sections 3.2.1 to 3.2.2 and sections 3.2.4 and 3.2.6. Basically, you will be creating a backup of your primary and creating a standby control file. Put the backup on your standby host and replace the control files with the standby controlfile. Then STARTUP MOUNT your standby under the correct version. Then start managed recovery and you're back in business!