One, DB default character set Al32utf8
Specify the database character set when you create the database. Starting from Oracle Database 12c Release 2, if you use Oracle Universal Installer (OUI) or Oracle database Configuration Assistant (DBCA) to create a database and then the default database character set used is the Unicode character set Al32utf8.
In databases prior to 12.2, the default character set for a database is determined by the operating system's character set. In 12.2, when the database is installed, the default character set for the database is Al32utf8.
Second, the PDB supports different character sets
There are several prerequisites for per-pdb Character set:
1) CDB must be Al32utf8
2) application Container requires single character set
3) national character set also supported per PDB
4) Truncation of data can occur in Cross-container queries if data conversion to UNICODE causes expansion
Introducing new features from 12.2 each PDB in the same CDB can use a different character set, provided the CDB is Al32utf8. such as CDB is Al32utf8, wherein the PDB1 is ZHS16GBK, from other CDB plug-in a different character set of the PDB is also allowed, in the plug-in PDB process does not convert the character set.
Oracle 12C new features DB default character set Al32utf8, PDB supports different character sets