The PDL header
The PDL begins with a two-word header. The DSECT= operand of the IKJPARM macro instruction provides a name for the DSECT created to map the PDL. Use this name as the symbolic address of the beginning of the PDL header.
| Offset decimal | Meaning |
|---|---|
| 0 | A pointer to the next block of virtual storage |
| 4 | Subpool number |
| 5 | Reserved |
| 6 | Length |
- Pointer to the next block of virtual storage:
- The Parse Service Routine gets virtual storage for the PDL and for any data received as the result of a prompt. Each block of virtual storage obtained begins with another PDL header. The blocks of virtual storage are forward-chained by this field. A forward-chain pointer of X'FF000000' in this field indicates that this is the last storage element obtained.
- Subpool number:
- This field will always indicate subpool 1. All virtual storage allocated by the Parse Service Routine for the PDL and for data received from a prompt is allocated from subpool 1.
- Length:
- This field contains a hexadecimal number indicating the length of this block of real storage (this PDL). The length includes the header.