Oracle 11g RAC - PSU
https://mikedietrichde.com/2017/04/26/keep-your-patch-versions-between-grid-infrastructure-and-databases-homes-in-synch/


  Can you have different PSU/BP versions between Database and GI homes?
  Yes, you can have a higher version PSU or BP in the Database home than
  in the Grid Infrastructure home managing the resources. This is
  implicitly documented in MOS Note 337737.1 – Oracle Clusterware
  (CRS/GI) – ASM – Database Version Compatibility where it says:
  
  “The Oracle Grid Infrastructure (GI) /Clusterware (CRS) version must
  be of the highest version down to the 4th digit in the possible
  combinations at all times.“
  
  Therefore you can deviate that this rule does not apply for the 5th
  digit anymore.