It is used for conversion between an input TCP CCSID and an output Host CCSID.
The valid encoding scheme for input data is X'5404'. The valid output encoding schemes are X'1100', X'1200', and X'1301'.
Input is always expected in a normalized four byte format, and includes the identifier in the high-order byte that indicates the coded graphic character set of the output code point.
The conversion table created will handle either single-byte, double-byte, or triple-byte code points from the input CS, CP pair as defined by the TCP encoding scheme to a possible single-byte, double-byte, or triple-byte output CS, CP code point.
The content of the table will reflect: - Matched GCGID priority within a CS, CP - Mismatch management criteria - Space character management.
For most TCP four-byte codes, only a certain range of values are valid for the three high-order bytes, causing the table to be organized as several subtables. Each of the subtables contains pointers to subsequent records in the table. Each of the subsequent records contains 256 double-byte output code point entries.
Invalid single-byte code points will be mapped into the single-byte character SUB, at code point X'3F'.
Invalid multi-byte input values will be mapped to the host double-byte SUB value of X'FEFE'.
Only a triple-byte CS, CP pair will use all four bytes of the four-byte input code point value.