Host Column Description Attributes

Attributes are shown in the following table.

Column Name

The column name attribute is the character string that represents the name of the column. This attribute may be null.

Alias

The alias attribute is an optional character string that represents an alias label for the column string name. This attribute may be null.

Precision

The precision is the total number of decimal digits in the column containing numeric data on the host. The only two fixed-point numeric data types that require this information are the NUMERIC and DECIMAL keyword data types, and for these types this field cannot be null and must contain a valid numeric value.

The precision must be set the same as the length attribute for CHAR and BINARY keyword data types, and set to zero for the other types. (Note that under ODBC, the precision was also used to indicate the length of nonnumeric data types including character, date, time, and binary data types.) Precision has no default value and must not be left null.

Scale

The scale is the number of decimal digits to the right of any decimal point for numeric data on the host. The only two numeric data types that require this information are the NUMERIC and DECIMAL keyword data types, and for these types this field cannot be null and must contain a valid numeric value. For other numeric (the SINGLE and DOUBLE keywords, for example) and nonnumeric data types (binary, character, date, time, and timestamp), the scale should be set to zero. This field must not be left null and must contain a numeric value.

Length

The length attribute is the total length of the data on the host. This field must not be left empty and must contain a numeric value.

Host Type

The Host Type attribute is a keyword value that represents the data type of the host data. This keyword value is based on standard data types used on AS/400 and VSAM files. If no keyword is entered, this attribute defaults to the BINARY keyword. The allowable types are as follows:

Host type name	Keyword	Comment
Binary	BINARY	Fixed-length binary data (no character code conversions). The length must be specified.
Character	CHAR	Fixed-length character data. The length must be specified.
Date	DATE	The date represented as character data in the format yyyy-mm-dd that fits in 10 bytes
DBCS - only	DBCS	Fixed-length character data that contain only DBCS data.
DCBS - Mixed Either	MIXED_EITHER	Fixed-length character data that can contain either DBCS or alphanumeric data.
DCBS - Mixed Open	MIXED_OPEN	Fixed-length character data that can contain both DBCS and alphanumeric data. DBCS data is distinguished from alphanumeric data with shift-control characters.
DBCS - Variable Only	VARDBCS	Variable-length character data with a prefix of 2 bytes for length that contains only DBCS data. The maximum possible length for the column containing this data type must be specified.
DCBS - Variable Mixed Either	VARMIXED_EITHER	Variable-length character data with a prefix of 2 bytes for length that can contain either DBCS or alphanumeric data. The maximum possible length for the column containing this data type must be specified.
DCBS - Variable Mixed Open	VARMIXED_OPEN	Variable-length character data with a prefix of 2 bytes for length that can contain both DBCS and alphanumeric data. DBCS data is distinguished from alphanumeric data with shift-control characters. The maximum possible length for the column containing this data type must be specified.
Double	DOUBLE	Floating-point data that fits in 8 bytes (64 bits)
Long	LONG	Integer data that fits in 4 bytes (32 bits)
Long Variable Binary	LONGVARBINARY	Variable-length binary data represented as an unsigned character array with prefix 2 bytes for length. The maximum possible length for the column containing this data type must be specified.
Long Variable Character	LONGVARCHAR	Variable-length character data with a prefix of 2 bytes for the length. The maximum possible length for the column containing this data type must be specified.
Packed	PACKED	Packed decimal numeric data where the precision, and scale are exactly as specified.
Short	SHORT	Integer data that fits in 2 bytes (16 bits)
Single	SINGLE	Floating-point data that fits in 4 bytes (32 bits)
Time	TIME	The time represented as character data in the format hh:mm:ss that fits in 8 bytes
Time Stamp	TIMESTAMP	Timestamp represented as characters in the format yyyy-mm-dd hh:mm:ss.ffffff that fits in 19 bytes
Variable Binary	VARBINARY	Variable-length binary data represented as an unsigned character array with prefix 2 bytes for length. The maximum possible length for the column containing this data type must be specified.
Variable Character	VARCHAR	Variable-length character data with a prefix of 2 bytes for length. The maximum possible length for the column containing this data type must be specified.
Zoned	ZONED	Zoned decimal numeric data where the precision and scale are exactly as specified.

Note that the OLE DB provider limits the maximum length character field that can be accessed on an AS/400 machine to 32,745. Attempting to access a character field greater than this length on an AS/400 machine can have unpredictable results and can cause the OLE DB Provider to hang.

Note that the floating-point data format assumed by the OLE DB Provider for AS/400 and VSAM depends on the host. For AS/400, the host floating-point data format is assumed to be IEEE. On mainframe hosts, floating-point data types are assumed to be in IBM floating-point formats. Since OLE DB supports the IEEE floating-point format, data conversion errors can occur when converting the extreme values of VSAM floating-point data in IBM format to IEEE floating-point data by the OLE DB provider.

Note that the DECIMAL, FLOAT, INTEGER, NUMERIC, REAL, and SMALLINT keywords should not be used in HCD files and should be replaced with the newer keywords as follows:

The DOUBLE keyword replaces the FLOAT keyword.

The LONG keyword replaces the INTEGER keyword.

The PACKED keyword replaces the NUMERIC keyword.

The SHORT keyword replaces the SMALLINT keyword.

The SINGLE replaces the REAL keyword.

The ZONED keyword replaces the DECIMAL keyword.

The SNA OLE DB Management Console snap-in will not work properly with HCD files containing these older keywords and will give unpredictable results.

OLE DB Type

The OLE DB Type attribute is a keyword that represents the data type of the local PC data. This keyword value is based on the standard OLE DB data types as defined in the OLEDB.H header file included with the OLE DB 1.5 SDK. The data structures for the date, time, and timestamp C data types are defined as typedefs in the OLEDB.H header file included with the OLE DB SDK. Similar data types are also used by ODBC. If no keyword is entered, this attribute defaults to the BINARY keyword.

For the decimal and numeric host data types, the OLE DB Type attribute must be set to DBTYPE_STR. These two fixed-point numeric types are currently converted to character data strings by the DDM layer of the Microsoft OLE DB Provider for AS/400 and VSAM. If these host types are converted to any of the defined OLE DB numeric C types, then numeric accuracy can be lost.

The allowable types are as follows:

OLE DB type name	Keyword	Comment
DBTYPE_BYTES	BINARY	Fixed-length binary data represented as an unsigned char array
DBTYPE_DBDATE	DATE	The OLE DB DBDATE typedef struct as defined in the OLEDB.H header file
DBTYPE_DBTIME	TIME	The OLE DB DBTIME typedef as defined in the OLEDB.H header file
DBTYPE_DECIMAL	DECIMAL	The OLE DB DECIMAL typedef struct as defined in the OLEDB.H header file.
DBTYPE_NUMERIC	NUMERIC	The OLE DB NUMERIC typedef struct as defined in the OLEDB.H header file.
DBTYPE_DBTIMESTAMP	TIMESTAMP	The OLE DB DBTIMESTAMP typedef struct as defined in the OLEDB.H header file
DBTYPE_I2	SHORT	Integer data stored in 2 bytes (16 bits)
DBTYPE_I4	LONG	Integer data stored in 4 bytes (32 bits)
DBTYPE_R4	FLOAT	Floating-point data stored in 4 bytes (32 bits)
DBTYPE_R8	DOUBLE	Floating-point data stored in 8 bytes (64 bits)
DBTYPE_STR	CHAR	Character data
DBTYPE_I1		Not supported (signed tiny integer stored in one byte, 8 bits)
DBTYPE_I8		Not supported (signed long long integer stored in eight bytes, 64 bits)
DBTYPE_UI1		Not supported (unsigned tiny integer stored in one byte, 8 bits)
DBTYPE_UI2		Not supported (unsigned short integer stored in two bytes, 16 bits)
DBTYPE_UI4		Not supported (unsigned long integer stored in four bytes, 32 bits)
DBTYPE_UI8		Not supported (unsigned long long integer stored in eight bytes, 64 bits)

Nullable

The Nullable attribute indicates whether this field can be a null value. Legal values for this field are Y or N. If this field is empty, the default value for nullable is N. The current version of the OLE DB Provider for AS/400 and VSAM does support nullable fields, so this value must be set to N.

CCSID

The Code Character Set Identifier (CCSID) attribute indicates the character set used on the host. If this field is empty, the default value for CCSID is set to EBCDIC US English (37). The CCSID setting used by the OLE DB Provider must bet set to match the CCSID actually used on the host otherwise data loss will occur. Note that some AS/400 systems default to a CCSID of 937 rather than 37 for enabling double-byte character sets (DBCS).

If the CCSID is set to 0 or 65535 then no character translation will take place when converting character data from the host to the PC by the OLE DB Provider. The allowable values for CCSID are as follows:

EBCDIC character set	CCSID value
U.S./Canada	37
Germany	273
Denmark/Norway	277
Finland/Sweden	278
Italy	280
Latin America/Spain	284
United Kingdom	285
France	297
International	500

Note that this value needs to correspond to the CCSID used on the host.

Title

The Title attribute is an optional character string that represents a comment describing the column. This attribute may be null.