Oracle Database Configuration Assistant (DBCA) can encounter the following error during creation of the Grid Infrastructure Management Repository (GIMR).

PRCD-1000 : Database _mgmtdb already exists

This could be due to an earlier failed repository creation.

Workaround:

Run following commands in Oracle Grid Infrastructure home:

srvctl stop mgmtdb -f
srvctl remove mgmtdb -f

During the creation of a pluggable database (PDB) from an existing PDB on Oracle Managed Files (OMF), you can edit the database ___location in the Oracle Database Configuration Assistant (DBCA) user interface. This enables you to change the ___location of the database files during PDB creation, implying that the ___location can be changed. This is incorrect because the PDB is always created with the database files in the same ___location as the source PDB, and you cannot modify the database ___location.

Workaround:

Do not edit the default database ___location value. OMF creates the new PDB with the default database ___location value only.