12c Container Database db_name conflicts with pdb name

Hello all,

I create some 12c Databases as Container database with pdbs.

The naming convention I plan to use is like

CDB-Name PDB-name

XXX_CDB  XXX

The dbca tool creates an internal 'db_name' for  the Container database itself, visible in the 'init.ora' file.

Nornmally it Looks like

XXX_ (note the trailing underscore)

Then I can create a PDB XXX without any Problems.

In one case the 'db_name' of the Container database itself is 'XXX' instead so I cannot creat a PDB named XXX.

Why could this be ?

Norbert