SNAP call facility

The SNAP call facility produces SNAP dumps of DL/I control blocks for the following items:

• External DL/I SNAP calls. The DL/I test program, DFSDDLT0, issues SNAP calls when it detects unequal conditions based on compare statements.
• Exceptional conditions, such as pseudoabends in DL/I modules and message or batch region abends.
• Internal SNAP requests from DL/I modules.
• SNAP specific requests from other IMS modules.

GSAM modules issue SNAP calls for GSAM databases. See GSAM control block dump - DFSZD510 for a description of the GSAM SNAP.

When a SNAP call is performed for a Fast Path region abend, module DFSERA20 bypasses some dumps:

• For a Fast Path database (an MSDB or DEDB), module DFSERA20 bypasses the DMB dump.
• For a DB PCB that refers to a Fast Path database, module DFSERA20 bypasses the DMB, DB PCB, JCB, and SDB dumps.

SNAP output consists of buffer pools and all PSB-related control blocks. Optionally, you can request subpools 0-127 in addition to the buffers and blocks.

SNAP output for exceptional conditions is always directed to the IMS log. In all other cases, IMS sends SNAP output to a data set identified on the PRINTDD DD statement. If this data set is not already open, it is opened and closed for each SNAP request. If you do not supply a PRINTDD statement, IMS sends the SNAP output to the IMS log as X'67FD' log records. When neither a SNAP data set nor the IMS log can be used for SNAPs, all SNAP actions are bypassed.

The File Select and Formatting Print utility (DFSERA10) extracts X'67FD' log records, and the exit routine (DFSERA30) formats them.

Status codes are not set for SNAP calls.