In order for SNAP to run, a system file with the name SNAPFILE must be created on the home pubset. It must be at least 16 MB in size and not larger than 1 GB. A value of at least 144 MB is recommended. It must not be copied from another pubset.
The SNAPFILE is installed during system generation using the SIR untility routine or when SNAP is activated using the ACTIVATE-SNAPSHOT command. It is cataloged under the TSOS user ID. During ongoing operation changes may be made to the SNAPFILE (configuration, changing size, deletion) only using the ACTIVATE-SNAPSHOT and DEACTIVATE-SNAPSHOT commands, see the “Commands” manual [8].
If the SNAPFILE is not available, it is created in the standard size when startup takes place (SNAP-ACTIVE-SWITCH=ON parameter) or in the specified size when the ACTIVATE-SNAPSHOT command is executed.
SNAP writes the diagnostic data to the SNAPFILE. To make sure that this file is emptied and thus available for subsequent SNAP calls, the SNAPFILE contents are automatically written to a dynamically generated system file after BS2000 is reactivated. This operation is given a high priority. These dump files are cataloged under the user ID SYSSNAP and are given the name
SNAP.snap-id.date.time
where: |
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The user ID SYSSNAP is created automatically during first startup.
The disk storage available for this ID should be at least twice as large as $TSOS.SNAPFILE.
The file $TSOS.SNAPFILE cannot be processed directly by any dump analysis routine. However, transferring the data from $TSOS.SNAPFILE to $SYSSNAP creates a file format that can be analyzed by the DAMP dump analysis routine. If the system is no longer able to transfer the file $TSOS.SNAPFILE to $SYSSNAP, $TSOS.SNAPFILE is automatically saved to an editable file under $SYSSNAP the next time the system is started up or at ACTIVATE-SNAPSHOT. In the case of a DRV home pubset, it is possible that the SNAPFILE can no longer be converted in the next session, and this half-finished SNAP dump is then lost.
The SNAPFILE file is discarded if it was created in the previous session within the framework of a system dump (CDUMP).
The SNAPFILE is only copied or converted when the SNAP function is activated.
No further SNAP calls are accepted until the SNAPFILE is emptied.