Header records

The record length of an external data file is the length of a row of the data, as described under Data records. The header records that precede the data records are also split into this length. Table 21 shows the information contained in the header records.

Table 21. Header record information
Byte Position Information and Type
1-8 QMF object format level (8 characters of data).

A QMF object format level specifies how many times the format has been updated for a particular object.

Because the form object has been altered three times since QMF 1.0, the object format level for a form exported from QMF 3.2 is 4. Because the data object format has not been altered, it is still at object format level 1.
9-10 Number of header records (halfword signed integer).
11-12 Number of data columns (halfword signed integer).
13-30, 37-54, ... Column name (18 characters of data).
31-32, 55-56, ... Data type (halfword signed integer). Data type codes are shown in Table 22.
33-34, 57-58, ... Column width (halfword signed integer). For most data types this is the width of the column in bytes. Exceptions are:
  • In DECIMAL columns, the first byte of the halfword represents the precision, and the second byte represents the scale.
  • In GRAPHIC and VARGRAPHIC columns, this value reflects the width of double-byte characters.
  • In FLOAT columns, this value is either 4, indicating single precision floating point, or 8, indicating double precision floating point.
35, 59, ... Nulls allowed: Y if nulls are allowed; N if they are not allowed (1 character of data).
36, 60, ... Unused byte.

Bytes 11-12 indicate the number of columns; this means that the information in bytes 13 through 36 is repeated for each column in the header records. Each column requires 24 bytes in the header record.

The data type codes are shown in Table 22.

Table 22. Data type codes
Code in Hexadecimal Code in Decimal Data Type Meaning
X'180' 384 DATE Date
X'184' 388 TIME Time
X'188' 392 TIMESTAMP Time stamp
X'1C0' 448 VARCHAR Varying character
X'1C4' 452 CHAR Fixed character
X'1D0' 464 VARGRAPHIC Varying graphic
X'1D4' 468 GRAPHIC Fixed graphic
X'1E0' 480 FLOAT Floating point
X'1E4' 484 DECIMAL Decimal
X'1F0' 496 INTEGER Integer
X'1F4' 500 SMALLINT Small integer

Date, time, and time stamp data is always exported in ISO format.

For more details of the format of data types, refer to DB2 UDB for OS390 SQL Reference.

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