The Oracle database uses the database character set for data stored in SQL CHAR data types (CHAR, VARCHAR2, CLOB, and LONG), for identifiers such as table names, and for SQL statements and PL/SQL source code. Only single-byte character sets and varying-width character sets that include either ASCII or EBCDIC characters are supported as database character sets. Multibyte fixed-width character sets (for example, AL16UTF16) are not supported as the database character set.
An alternative character set can be used in the database for data stored in SQL NCHAR data types (NCHAR, NVARCHAR2, and NCLOB). This alternative character set is called the database national character set. Only Unicode character sets are supported as the database national character set.