Validating Control Blocks

The process of validating one control block and following its pointers to other control blocks is called a scan probe. To do a scan probe, use the SCAN subcommand.

IPCS initiates SCAN subcommand processing from the storage map. SCAN validates control blocks that are listed in the storage map and that are within the specified address range. As it does this, SCAN makes new map entries for control blocks, modules, and areas pointed to by the block being validated. SCAN always has storage map entries to work with because dump initialization creates the original entries for a dump.

Suppose the map for a new dump contains only the entries for the CVT and the private area. To make one pass through the storage map, enter:

scan

If SCAN finds a structure that it maps, SCAN validates it. SCAN never validates a specific storage map entry a second time. Subsequent passes through the map only validate those entries not already completely validated.

If a large number for the DEPTH parameter were used in the above example, one scan probe could map all the areas and control blocks in a dump.