When the primary database tries to perform a backup, it will find out its meta data is different from the catalog and asks for DBA's intervention before doing any further backup. In such case, you can perform a crosscheck to work around it.
RMAN> crosscheck archivelog all;
For resolving the confusion, Oracle uses a new parameter called DB_UNIQUE_NAME since 10g onward to distinguish the databases that share the same DBID. More examples can be found in the following link:
12 Using RMAN to Back Up and Restore Files