Saving a db-key

Navigational DML Programming Techniques › Saving db-key, Page Information, and Bind Addresses › Saving a db-key

Saving a db-key

You can retrieve a db-key using one of these methods:

Accepting the db-key of a current record. You can retrieve the db-key of the record that is current of run unit, record type, set, or area using the ACCEPT DB-KEY FROM CURRENCY statement.
Note: You can also retrieve the db-key of the record that is current of run unit from the DBKEY field of the IDMS communications block. You can retrieve its page information from the PAGE-INFO field of the IDMS communications block.
Accepting a db-key relative to the current record. You can use an ACCEPT DB-KEY RELATIVE TO CURRENCY statement to retrieve the db-key of the NEXT, PRIOR, or OWNER record relative to the current record of set.

Steps in Saving a db-key

To save a db-key, perform the following steps:

Establish the appropriate currency for the required record.
Perform one of the following steps:
- If the required record is current of run unit, move the DBKEY field in the IDMS communications block to a variable storage field defined as a binary fullword (COBOL PIC S9(8) COMP SYNC).
- If the required record is not current of run unit, issue either the ACCEPT DBKEY FROM CURRENCY or the ACCEPT DBKEY RELATIVE TO CURRENCY statement, storing the saved db-key in a variable storage field defined as a binary fullword (COBOL PIC S9(8) COMP SYNC).
Perform the IDMS-STATUS routine if the DBMS returns a nonzero value.

Important! You should not save db-keys or page information outside of the program because these values can change if the database is unloaded and reloaded, if record occurrences are erased or if an area is assigned to a different page group.

Example of Using db-keys

The program excerpt below shows a program that compares db-keys. The first db-key is acquired from the IDMS communications block, the second by using an ACCEPT DB-KEY statement.

This application compares the db-key of each JOB record with JOB owner db-keys in EMPOSITION records in the JOB-EMPOSITION set. When the db-keys match, the program accesses the EMPOSITION information by issuing a GET statement.

 WORKING-STORAGE SECTION.
 01  JOB-DBKEY          PIC S9(8)  COMP.
 01  MATCH-DBKEY        PIC S9(8)  COMP.
 .
 .
 .
 PROCEDURE DIVISION.
 .
 .
 .
     PERFORM A100-GET-EMP-JOB THRU A100-EXIT
          UNTIL END-OF-FILE.
 .
 .
 .
 A100-GET-EMP-JOB.
     MOVE GETEMP-ID-IN TO EMP-ID-0415.
     OBTAIN CALC EMPLOYEE.
*** CHECK FOR ERROR-STATUS = 0326 ***
     IF DB-REC-NOT-FOUND
       DISPLAY 'EMP NOT FOUND: ' GETEMP-ID-IN
       GO TO A100-GET-NEXT
*** CHECK FOR ERROR-STATUS = 0000 ***
     ELSE IF DB-STATUS-OK
       NEXT SENTENCE
     ELSE
       PERFORM IDMS-STATUS.
     MOVE GETJOB-ID-IN TO JOB-ID-0440.
     OBTAIN CALC JOB.
*** CHECK FOR ERROR-STATUS = 0326 ***
     IF DB-REC-NOT-FOUND
       DISPLAY 'JOB NOT FOUND: ' GETJOB-ID-IN
       GO TO A100-GET-NEXT
*** CHECK FOR ERROR-STATUS = 0000 ***
     ELSE IF DB-STATUS-OK
       NEXT SENTENCE
     ELSE
       PERFORM IDMS-STATUS.
*** SAVE JOB DB-KEY ***
     MOVE DBKEY TO JOB-DBKEY.
     IF EMP-EMPOSITION IS EMPTY
         DISPLAY 'EMP-EMPOSITION IS EMPTY FOR: ' GETEMP-ID-IN
         GO TO A100-GET-NEXT
     ELSE
         PERFORM A200-LOOP THRU A200-EXIT.

 A100-GET-NEXT.
     READ GET-FILE-IN AT END MOVE 'Y' TO EOF-SW.
 A100-EXIT.
     EXIT.
 A200-LOOP.
     FIND NEXT WITHIN EMP-EMPOSITION.
*** CHECK FOR ERROR-STATUS = 0307 ***
     IF DB-END-OF-SET
        GO TO A200-EXIT
*** CHECK FOR ERROR-STATUS = 0000 ***
     ELSE IF DB-STATUS-OK
        NEXT SENTENCE
     ELSE
        PERFORM IDMS-STATUS.
*** ACCESS DB-KEY OF OWNER IN JOB-EMPOSITION SET ***
     ACCEPT MATCH-DBKEY FROM JOB-EMPOSITION
           OWNER CURRENCY.
     IF DB-STATUS-OK
        NEXT SENTENCE
     ELSE
        PERFORM IDMS-STATUS.
*** IF DB-KEYS ARE NOT EQUAL, LOOP AND TRY AGAIN ***
     IF JOB-DBKEY NOT = MATCH-DBKEY
       THEN
         GO TO A200-LOOP
     ELSE
        NEXT SENTENCE.
*** IF DB-KEYS ARE EQUAL, ACCESS THE EMPOSITION DATA ***
     GET EMPOSITION.
     IF NOT DB-STATUS-OK
       PERFORM IDMS-STATUS
     ELSE NEXT SENTENCE.
     PERFORM A300-PRINT-DATA.
 A200-EXIT.
     EXIT.
 .
 .
 .

Inferring Information

For indexed sets and chained sets with prior pointers, the ACCEPT DB-KEY RELATIVE TO CURRENCY statement can also be used to infer information, as shown in the program excerpt below.

This application erases all DEPARTMENT records that contain less than two EMPLOYEE records. The first ACCEPT statement tests for zero EMPLOYEE records; the second ACCEPT statement tests for one.

 WORKING-STORAGE SECTION.
 01  SAVED-DBKEYS.
     05 NEXT-DEPT-EMP-DBKEY     PIC S9(8) COMP SYNC.
     05 PRIOR-DEPT-EMP-DBKEY    PIC S9(8) COMP SYNC.
 PROCEDURE DIVISION.
 A100-LEAN-AND-FAST.
     OBTAIN FIRST DEPARTMENT WITHIN ORG-DEMO-REGION.
*** CHECK FOR ERROR-STATUS = 0307 ***
     IF DB-END-OF-SET THEN
        GO TO EMPTY-AREA
     ELSE
        PERFORM IDMS-STATUS.
     PERFORM A200-ACCEPT-AND-TEST THRU A200-EXIT
                  UNTIL DB-END-OF-SET.
     FINISH.
     GOBACK.
 A200-ACCEPT-AND-TEST.
*** RETRIEVE NEXT DB-KEY ***
     ACCEPT NEXT-DEPT-EMP-DBKEY FROM
        DEPT-EMPLOYEE NEXT CURRENCY.
        PERFORM IDMS-STATUS.
*** CHECK FOR EMPTY SET ***
*** IF DB-KEYS ARE THE SAME, THE SET IS EMPTY ***
     IF NEXT-DEPT-EMP-DBKEY = DBKEY THEN
        ERASE DEPARTMENT PERMANENT
        PERFORM IDMS-STATUS
        GO TO A200-GET-NEXT.
*** CHECK FOR ONE-MEMBER SET ***
     ACCEPT PRIOR-DEPT-EMP-DBKEY FROM
            DEPT-EMPLOYEE PRIOR CURRENCY.
     PERFORM IDMS-STATUS.
*** IF DB-KEYS ARE THE SAME, THE SET HAS ONE MEMBER ***
     IF NEXT-DEPT-EMP-DBKEY =
               PRIOR-DEPT-EMP-DBKEY THEN
        ERASE DEPARTMENT PERMANENT
        PERFORM IDMS-STATUS
        GO TO A200-GET-NEXT
     ELSE
        GO TO A200-GET-NEXT.
 A200-GET-NEXT.
     OBTAIN NEXT DEPARTMENT WITHIN ORG-DEMO-REGION.
*** CHECK FOR ERROR-STATUS = 0307 ***
     IF DB-END-OF-SET THEN
        GO TO A200-EXIT
     ELSE
        PERFORM IDMS-STATUS.
 A200-EXIT.
     EXIT.