Oracle Error Message
RMAN-20018: database not found in recovery catalog
Reason for the Error
An attempt was made to grant or revoke catalog access to a database whose name was not registered in the recovery catalog.
Solution
Correct the database name and re-issue the GRANT or REVOKE command. If this is an attempt to grant or revoke access to a database that is not yet registered, then re-issue the command using the database ID of the desired database.