Example 1: Setting the national character set for an interactive
    session

    SQL> show character sets;
    Default character set is DEC_KANJI
    National character set is DEC_MCS
    Identifier character set is SHIFT_JIS
    Literal character set is SHIFT_JIS
    Display character set is SHIFT_JIS
    SQL> set national character set 'DEC_KANJI';
    SQL> show character sets;
    Default character set is DEC_KANJI
    National character set is DEC_KANJI
    Identifier character set is SHIFT_JIS
    Literal character set is SHIFT_JIS
    Display character set is SHIFT_JIS