Rman Catalog Sync Internal Error

Symptom:

 RMAN>  resync catalog;

starting partial resync of recovery catalog
RMAN-00571: ==============================================
RMAN-00569: ======== ERROR MESSAGE STACK FOLLOWS ========
RMAN-00571: ===============================================
RMAN-03009: failure of resync command on default channel at 04/04/2018 19:01:45
RMAN-20999: internal error

Solution:

Use  rman trace=mytrace.log debug target /

find some datafile info inconsistent on catalog DB. see note Doc ID 2240323.1
 

One quick solution is to drop and recreate catalog
RMAN> drop catalog;

RMAN> create catalog;

RMAN> register database;