UPGRADE RMAN CATALOG FROM 11G TO 12C

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UPGRADE  CATALOG  RMAN FROM 11G TO  12C
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The doc tells you to run this step first:

SQL> @$ORACLE_HOME/rdbms/admin/dbmsrmansys.sql

Please ignore the "-all" option printed in the doc - this is a known docu bug
If you miss this step the upgrade of the catalog will fail with a warning that your user lacks privileges
$ rman CATALOG my_catalog_owner@catdb
recovery catalog database Password:
RMAN> UPGRADE CATALOG;
RMAN> EXIT;
It should work now :-)