Multiple qualification statements for HDAM, PHDAM, or DEDB

For HDAM (Hierarchical Direct Access Method), PHDAM (partitioned HDAM), or data entry database (DEDB) organizations, a randomizing exit routine usually does not store the root keys in ascending key sequence. For these organizations, IMS determines the minimum and maximum key values. The minimum key value is passed to the randomizing exit routine, which determines the starting anchor point.

The first root off this anchor is the starting point for the search. When IMS encounters a key that exceeds the maximum key value, IMS terminates the search with a GE status code. If the randomizing routine randomized so that the keys are stored in ascending key sequence, a call for a range of keys will return all of the keys in the range. However, if the randomizing routine did not randomize into key sequence, the call does not return all keys in the requested range. Therefore, use calls for a range of key values only when the keys are in ascending sequence (when the organization is HDAM, PHDAM, or DEDB).

Recommendations:
  • When the organization is HDAM, PHDAM, or DEDB, use calls for a range of key values only when the keys are in ascending sequence.
  • When the organization is HDAM, PHDAM or DEDB, do not use calls that allow a range of values at the root level.

While not recommended, a sequential search of the database can be accomplished with the use of command codes A and G when making GN/GHN database calls. Command code A will clear positioning and cause the call to start at the beginning of the database. Command code G will prevent randomization and cause a sequential search of the database when used with SSAs that specify a range of values at the root level. The returned segments may not be in sequential order depending on how they were randomized.

To search the database sequentially, you can use the use the following segment search argument (SSA) together with SSAs that specify a range of values at the root level. 
 key field > hex zeros & key field < all f's key
The returned segments may not be in sequential order depending on how they were randomized.

For more details about HDAM or PHDAM databases, see IMS Version 15.4 Database Administration.