PDB_PLUG_IN_VIOLATIONS is a dictionary view for displaying incompatible information or violations about the PDB to the CDB which it plugs in.
In fact, before you look up PDB_PLUG_IN_VIOLATIONS, the very first error message you saw could be at opening the PDB:
SQL> alter pluggable database ORCLPDB open;
Warning: PDB altered with errors.
To solve "Warning: PDB altered with errors.", we have 2 cases for you.
- SQL patch level mismatch
- Common user's default tablespace
You may have a look.