How the Allocation Exit Executes
The allocation exit executes in the DTF address space when the following conditions exist:
- The allocation exit is specified in the initialization parameters.
- A file is being received, and the Process step that initiated the copy is not in restart mode.
The following figure illustrates the structure of the parameter list for the allocation exit.
The following table is a list of the allocation exit parameters.
|R1||Register 1 that contains the address of a standard parameter list upon entry into the user-written allocation exit|
|PLIST||Stands for standard parameter list|
|SQCB||Security control block|
|VSAMPL||Stands for VSAM parameter list, whose address is the first full word in the PLIST|
|VSCCBADR||Address of the Process step header and is contained in VSAMPL|
|TCQSH||Process step header portion of the Copy control block (each step of a Process generates a TCQSH)|
|SDESCR||Source data set descriptor portion of the Copy control block|
|DDESCR||Destination data set descriptor portion of the Copy Control Block (a sample of the DDESCR Control Block is included in this section)|
The following macros map the control block structures.
|DGA$VSMP||Macro that defines the VSAMPL control block|
|DGA$TQSH||Macro that defines the TCQSH portion of the Copy control block|
|DGA$SDCR||Macro that defines the SDESCR portion of the Copy control block|
|DGA$DDSR||Macro that defines the DDESCR portion of the Copy control block|