When use RMAN duplicate command to create a copy of source database on a different host or a physical standby database, usually we specify the option “NOFILENAMECHECK” to avoid error messages.

However an interesting thing is that starting from Oracle 19c – 19.2.0.0.0, you will see a warning message

RMAN-05158: WARNING: auxiliary (datafile) file name <file name> conflicts with a file used by the target database

if “NOFILENAMECHECK” is used.

Apparently Oracle has thought the option is dangerous and wanted to give a warning so that users do the due diligence to make sure the target (source) database is safe.

So if the auxiliary database is on a different host, and there is NO shared volumes etc, the warning message can be ignored.

• Oracle