|DB2 now supports new collation sequence keywords, IDENTITY_16BIT and |SQL_CS_IDENTITY_16BIT, for Unicode databases. When IDENTITY_16BIT is |specified for the CLP CREATE DATABASE command or SQLEDBDESC.SQLDBCSS is |set to SQL_CS_IDENTITY_16BIT in the sqlecrea() -- Create Database API, |all data in the Unicode database will be collated using the CESU-8 |order. CESU-8 is Compatibility Encoding Scheme for UTF-16: |8-Bit, and as of this writing, its specification is contained in the |Draft Unicode Technical Report #26 available at the Unicode Technical |Consortium web site(www.unicode.org). CESU-8 is binary |identical to UTF-8 except for the Unicode supplementary characters, that is, |those characters that are defined outside the 16-bit Basic Multilingual Plane |(BMP or Plane 0). In UTF-8 encoding, a supplementary character is |represented by one 4-byte sequence, but the same character in CESU-8 requires |two 3-byte sequences.
|In a Unicode database, CHAR, VARCHAR, LONG VARCHAR, and CLOB data are |stored in UTF-8, and GRAPHIC, VARGRAPHIC, LONG VARGRAPHIC, and DBCLOB data are |stored in UCS-2. For IDENTITY or SQL_CS_NONE collation, |non-supplementary characters in UTF-8 and UCS-2 have identical binary |collation, but supplementary characters in UTF-8 collate differently from the |same characters in UCS-2. IDENTITY_16BIT or SQL_CS_IDENTITY_16BIT |ensures all characters, supplementary and non-supplementary, in a DB2 Unicode |databases have the same binary collation.