SNAPs on exceptional conditions

IMS produces SNAPs of DL/I control blocks on the IMS log (or the CICS® system log).

The SNAP call facility identifies calling routines that generate snap dumps. Supervisor call (SVC) dumps are generated only for the intended abend codes or status codes, and for unknown calling routines.

IMS produces SNAPs of DL/I control blocks on the IMS log (or the CICS system log) in the following exceptional situations:

• A pseudoabend condition is encountered in a DL/I module.
• A system or user abend occurs for either a message region or a batch message region.

Control block SNAPs are produced in the same format as those produced by a DL/I SNAP call specifying ALL or YYY as SNAP options.

The SNAP IMS log records are record type X'67', subrecord type X'FF'. You can select these log records from the IMS log with the File Select and Formatting Print utility (DFSERA10). You can format output selected from the log with the formatting edit routine DFSERA30.

Internal IMS functions can request the snapping of specific virtual storage areas by issuing a SNAP Specific call to DFSERA20.

The following IMS functions request or use the SNAP Specific facility:

• SBSNAP option, on completion of calls from IMS modules to the Sequential Buffering buffer handler
• SBESNAP option, during SB evaluation
• SB COMPARE option, when detecting a mismatch between the buffer content that the SB buffer handler was returning to the OSAM buffer handler and the content of the database block as it is stored on DASD

For IMS online regions and CICS, these SNAPs are written to the IMS log. For IMS batch regions, these SNAPs can be written to either the log or to a data set specified on another DD statement.

When written to the log, the IMS log records have a record type X'67' and a subrecord type X'E'. The value of the low-order half-byte of the subrecord type depends on the IMS function that requests the SNAP. The subrecord types are:

X'ED'

SBESNAP option

X'EE'

SBSNAP option

X'EF'

SB COMPARE option

The formatting edit routine DFSERA30 can format output selected from the log.