When you connect to your RMAN catalog and receive the following error, usually after a database upgrade:

"RMAN.DBMS_RCVCAT / CAT.DBMS_RCVMAN version in RCVCAT database is not current error".

[oracle@localhost ~]$ rman target sys/** catalog cat/**@CAT

Recovery Manager: Release 19.0.0.0.0.0 - Production on Thu Aug 15 18:30:27 2024
Version 19.21.0.0.0.0

Copyright (c) 1982, 2019, Oracle and/or its affiliates. All rights reserved.

Connected to target database: TESTING (DBID=1956950329
Connected to recovery catalog database
package PL/SQL package .DBMS_RCVCAT, version 19.17.00.00, in the RCVCAT database is not current
package PL/SQL package .DBMS_RCVMAN, version 19.17.00.00, in the RCVCAT database is not current

Simply run the command (upgrade catalog). Depending on the version, as in our case, you will have to run it twice.

RMAN> upgrade catalog
The recovery catalog owner is RCAT
Enter the UPGRADE CATALOG command again to confirm the catalog upgrade
RMAN> upgrade catalog
The recovery catalog has been upgraded to version 19.21.00.00.00
package DBMS_RCVMAN package to version 19.21.00.00
package DBMS_RCVCAT package to version 19.21.00.00.