A program can request a SNAP dump at any time during its processing by issuing a SNAPX or SNAP macro. For a SNAP dump, the DD statement can have any name except SYSABEND, SYSMDUMP, and SYSUDUMP.
If your program is in AR ASC mode, use the SNAPX macro instead of SNAP. Ensure that the SYSSTATE ASCENV=AR macro has been issued to tell the macro to generate code and addresses appropriate for callers in AR mode.
Like the ABEND dump, the data set containing the dump can reside on any device that is supported by BSAM. The dump is placed in the data set described by the DD statement you provide. If you select a printer, the dump is printed immediately. However, if you select a direct access or tape device, you must schedule a separate job to obtain a listing of the dump, and to release the space on the device.
To obtain a dump using the SNAP macro, you must provide a data control block (DCB) and issue an OPEN macro for the data set before issuing any SNAP macros. If the standard dump format is requested, 120 characters per line are printed. The DCB must contain the following parameters: DSORG=PS, RECFM=VBA, MACRF=W, BLKSIZE=882 or 1632, and LRECL=125. (The DCB is described in z/OS DFSMS Using Data Sets, and z/OS DFSMS Macro Instructions for Data Sets). If a high-density dump is to be printed on a 3800 Printing Subsystem, 204 characters per line are printed. To obtain a high-density dump, code CHARS=DUMP on the DD statement describing the dump data set. The BLKSIZE= must be either 1470 or 2724, and the LRECL= must be 209. CHARS=DUMP can also be coded on the DD statement describing a dump data set that will not be printed immediately. If CHARS=DUMP is specified and the output device is not a 3800, print lines are truncated and print data is lost. If your program is to be processed by the loader, you should also issue a CLOSE macro for the SNAP DCB.