Change rman backup retention

Hello everyone,

I am using rman backup with Oracle 11.2.0.3. I am trying to reduce the backup retention from 40 day to 22. I changed parameter "control_file_record_keep_time" both in DB and DB17. I also set expire_period to the same value in initSID.sap. When I run the backup, I get the following error:

BR0187E Value 22 of parameter/option 'control_file_record_keep_time' smaller than 30.

Does anyone know how to fix this?

Thanks