Last week I was testing our backups and got this error: ORA-15204: database version 126.96.36.199.0 is incompatible with diskgroup DATA_EDT1. This surprised me because all of our databases and Oracle homes on this Exadata are at version 188.8.131.52. I was testing full restore/recovery without a control file or an spfile. The first step was to restore spfile and controlfile from autobackup to their ASM locations.
I queried V$ASM_DISKGROUP in ASM and saw that all of our diskgroups have compatibility set to 184.108.40.206.0. In order to start RMAN restore I had created a minimal pfile. I didn’t bother setting the compatible parameter. I edited the pfile and set compatible=”220.127.116.11.0″ – that fixed it and the restore/recovery worked fine.