Concepts › CA IDMS Extractor Database Paths › Recursive Data Structures

Recursive Data Structures

A structure is considered to be recursive if a record type is retrieved by more than one set type in the same path. A Bill-of-Materials (BOM) structure is an example of a recursive structure.

CA IDMS Extractor lets you know that a recursive structure is in the path once you reach the Record Level Selection Criteria screen when a record type is retrieved a second or more time in the same path.

The following fields appear on the Record Level Selection Criteria screen only when a record type is retrieved a second or more time in the same path:

• EXTRACT ALL OWNERS OF EXTRACTED RECURSIVE RECORDS?===> is displayed if the current record is recursive and the set is walked member to owner. You must tell CA IDMS Extractor whether to extract all of the record's owners.

  This action imposes a great deal of overhead. Enter an N in this field if you are certain that the owner records of all extracted recursive records are extracted because they are retrieved via some OTHER SET in your path definition. Otherwise, your target database will NOT be complete.

• NUMBER OF LEVELS TO EXTRACT IN THE RECURSIVE STRUCTURE===> In most recursive structures, this value should be set to zero (0), except for true BOM structures. Your situation may dictate otherwise. You must be aware, however, of the additional overhead needed to process recursive structures.

In the simplified data structure diagram shown below, the structure in Example 1 contains a BOM structure. In both examples, Record A is an Entry Record and SETS AB and BC1 are selected walking from owner to member. After defining Record Level Selection Criteria for record C as a member of the BC1 set, SET BC2 is selected walking from member to owner in Example 1. Set CA is selected walking owner to member in Example 2.

At this point, CA IDMS Extractor determines that Record B in Example 1 and Record A in Example 2 participate in recursive structures and are regarded as recursive records. These records/sets define the beginning of the recursive structure. You must tell CA IDMS Extractor how many times the recursive structure is to be walked once the beginning of the recursive structure is found.

In these examples, once Record B is retrieved through set BC2 and Record A is retrieved through set CA, you must tell CA IDMS Extractor how many more times sets selected in the path after Record B in Example 1 and Record A in Example 2 are to be walked. Specifying zero (0) in the NUMBER OF LEVELS TO EXTRACT IN THE RECURSIVE STRUCTURE field tells CA IDMS Extractor to not retrieve any more records/sets in the path at that point.

For each recursive record that is extracted, CA IDMS Extractor also extracts all owners of selected sets in which the recursive record is currently a member. In these examples, after Record B is retrieved and extracted through set BC2, CA IDMS Extractor extracts the owning Record A even though set AB is being walked from owner to member.

You may specify a value for NUMBER OF LEVELS TO EXTRACT IN THE RECURSIVE STRUCTURE that is greater than the actual number of levels present in your database. CA IDMS Extractor uses this value as the maximum number of levels that it traverses.