Do not change the instructions that define the block header unless
you want to put extra information in the extended header in each prime
block (see Optimizing the database design). You can do this after
the standard z/TPFDF header
field.
Figure 1 shows a block header for a
DSECT that uses fixed-length or variable-length LRECs and that uses
4-byte file addresses (DBDEF macro HDR parameter specifies 4BYTEFA). Figure 1. Instructions in a DSECT macro to define the file
header with 4-byte file addresses
***********************************************************************
* STANDARD TPFDF HEADER *
***********************************************************************
SAM3HDR&CG1 DS CL16 STANDARD FILE HEADER
DS CL10 STANDARD TPFDF HEADER
SAM3VAR&CG1 EQU * START OF VARIABLE USER-AREA
SAM3HDL&CG1 EQU SAM3VAR&CG1-SAM3HDR&CG1 HEADER-LENGTH UP TO SAM3VAR
For z/TPFDF files
using 8-byte file addresses (DBDEF macro HDR parameter specifies 8BYTEFA),
the block header for the DSECT is shown by Figure 2. Figure 2. Instructions
in a DSECT Macro to define the file header with 8-byte file addresses
***********************************************************************
* STANDARD TPFDF HEADER *
***********************************************************************
SAM3HDR&CG1 DS CL32 STANDARD FILE HEADER
DS CL16 STANDARD TPFDF HEADER
SAM3VAR&CG1 EQU * START OF VARIABLE USER-AREA
SAM3HDL&CG1 EQU SAM3VAR&CG1-SAM3HDR&CG1 HEADER-LENGTH UP TO SAM3VAR