Coding Specialized Routines › Snap Facility

Snap Facility

Use the SNAP facility when the Reporting Facility detects a program check interruption during the execution of the generated machine code. To initiate the SNAP facility, use the following command:

►►─ OPTION ─ SNAP ─ n ─ m ────────────────────────────────────────────────────►◄

n

Specifies the number of the program check to print, (2 will print every other SNAP and 10 will print every tenth SNAP).

m

Specifies the sequential number of the program check to abend and terminates processing with a full system dump.

The SNAP routines output the following information when a program check occurs. This information can be used to determine if the problem is with the data or is an internal software problem.

• PSW expanded to show components
• 16 general registers
• Save area register stack
• Linkage section for main program
• Linkage section for control program
• GSA
• I/O area for user exit
• Standard I/O buffer area
• Generated code for this phase

When used in a z/OS environment, the system directs output from the SNAP facility to the DRSNAP data set, which the system assumes is a system printer. For example:

 //DRSNAP DD SYSOUT=*

In a z/VSE environment, the system directs the output to the DRSNAP data set, which it assumes is a sequential data set. This sequential file contains 132-byte records and is blocked at 1320. Each record consists of a single standard carriage control character, and a 131-byte print line image.

You can then read this file and print it with a special utility program. For example:

 // DLBL DRSNAP,'datasetname',0,SD
 // EXTENT SYSnnn,1,0,nnnn,nnn

The Reporting Facility can read this file and will print it.