Retrieving LRF-Based Records

To retrieve LR records, the data adapter sends LRF calls to an access module named IDMS that invokes Logical Record Facility program.

LRF-based records are retrieved when the Access File specifies MODE=LR in the subschema declaration and the data adapter constructs an LR call to IDMS with explicit or implicit selection criteria from the request. The LRF processes the request as generated by the data adapter, selects the appropriate LR path, and constructs each flat view using the full set of selection criteria. The process is highly efficient in terms of I/O; only those records that pass the selection tests are passed back to the data adapter from IDMS.

The retrieval process for LRF records is identical to that of network record-types, but the Logical Record Facility maintains its own navigational information for the data source, selects the retrieval strategy most appropriate for a given request, and maintains its own set of currencies.

When the subschema mode is Logical Record (MODE=LR), the data adapter analyzes the request and creates an LRF command to be sent to the Logical Record Facility. The LRF command has two formats. The first format is for an entry segment without selection criteria:

OBTAIN NEXT record

The second format is for an entry with selection criteria or for a descendant segment:

OBTAIN NEXT record WHERE expression1 [AND expressionn]

As indicated by the brackets, this command is also used to pass compound selection criteria to IDMS.

IDMS processes the call and returns a record if two conditions are met:

There is a SELECT path in the LR path-group that can process the particular request. (For entry segments without selection criteria, there must be a null SELECT clause defined for the logical record.) If there is no available SELECT path, IDMS returns error message 2041, and the data adapter terminates its processing with a FOC949 error message.

(FOC949) THE NUMBER OF SORT FIELDS EXCEEDS THE MAXIMUM:

A total of (32+number of common BY fields-number of PRINT (LIST) verbs-number of no BY verbs) BY phrases can be used in MATCH request at one time. Common BY fields are any subsequence of the largest consistent MATCH sort key set.

There is a complete LRF record created by the path-group logic. If the selected path-group can return partial records, the data adapter processes returned records until the first partial record is returned and the LR status field is not LR-FOUND or LR-NOT-FOUND. When the data adapter encounters any other status in the LR status field, it aborts the record retrieval process and returns error messages FOC967 and FOC949. Logical records that allow retrieval of partial records should not be used with the data adapter.

(FOC967) DATA SET NOT ALLOCATED/BAD ALLOCATION

TSO IEDIT: error happened while allocating the data set to be edited. Check data set name, ddname, DYNAMNBR parameter in logon procedure.

(FOC949) THE NUMBER OF SORT FIELDS EXCEEDS THE MAXIMUM:

The data adapter continues to call IDMS for LRF records that correspond to a segment until IDMS returns LR-NOT-FOUND in the LR status field. Then the data adapter retrieves records for other segments, or it terminates retrieval and the report is produced.

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