CKDELETE

Operation Notes

In order to delete a record, you should first read the record into the working storage section of your program with a call to CKREAD if in sequential mode, a call to CKREADBYKEY if in random mode, or a call to either if in dynamic mode. CKDELETE can be called only if the file is currently open for both input and output (input/output type =2). This allows the record to be read into your program's data area and then written back to the file with the delete mark. Following execution of CKDELETE, the deleted record can no longer be accessed.

If the file was opened for shared access with CKOPENSHR, you must lock the file with CKLOCK before you can delete any records with CKDELETE. Because CKDELETE depends on the logical record pointer, the call to CKLOCK should precede the call that positions the pointer. The call to CKUNLOCK is then called after the call to CKDELETE. To illustrate, the sequence of calls in shared access should be:

 
  CKLOCK <--- to lock file 
  CKSTART or CKREADBYKEY <--- to position pointer 
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  CKDELETE<--- to delete record at which pointer is positioned
  CKUNLOCK<--- to unlock file 

Following the call to CKDELETE, the pointer is positioned to the next key following the key in the deleted record.

The following examples show the use of CKDELETE for sequential access using CKREAD and for random access using CKREADBYKEY. The WORKING-STORAGE SECTION from Figure A-2 “Representation of KSAMFILE Used in COBOL Examples” and the FINISH procedure from the CKCLOSE example are assumed for these examples.

	NOTE: If access is shared, the file must be opened with a call to CKOPENSHR and then locked before the call to CKSTART that initially sets the pointer. The file must remain locked while the records to be deleted are read and then marked for deletion. If the file is not locked before CKSTART is called, other users can change the file so that the record pointer points to the wrong record.

In the first example, to delete all records whose primary key begins with "P", first position the file to the start of these records with CKSTART and then read each record with CKREAD and delete it with CKDELETE.

 
WORKING-STORAGE SECTION. 
77 RELOP PIC S9(4) COMP. 
77 KEYVAL PIC X(20). 
77 KEYLOC PIC S9(4) COMP. 
77 KEYLENGTH PIC S9(4) COMP. 
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PROCEDURE DIVISION. 
 
START.
 
 MOVE 2 TO I-O-TYPE. 
 MOVE 0 TO A-MODE. 
 CALL "CKOPEN" USING FILETABLE, STAT. 
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  FIND-REC. 
    MOVE 0 TO RELOP.<--- test for equality between
                           primary key and KEY 
    MOVE "P" TO KEYVAL. 
    MOVE 3 TO KEYLOC. 
    MOVE 1 TO KEYLENGTH.<--- check first character only 
    CALL "CKSTART" USING FILETABLE, STAT, RELOP, KEYVAL, KEYLOC, 
    KEYLENGTH. 
    IF STATUS-KEY-1 = "0" THEN 
      GO TO READ-REC. 
    IF STAT = "23" THEN 
      DISPLAY "NO RECORD FOUND" 
      GO TO FINISH. 
    IF STATUS-KEY-1 = "9" THEN 
      CALL "CKERROR" USING STAT, RESULT 
      DISPLAY "CKERROR NO.=", RESULT 
      GO TO FINISH. 
  READ-REC. 
    CALL "CKREAD" USING FILETABLE, STAT, REC, RECSIZE. 
    IF STATUS-KEY-1 = "1" THEN 
	DISPLAY "END OF FILE REACHED" 
	GO TO FINISH. 
    IF STATUS-KEY-1 = "0" THEN 
    IF NAME OF REC NOT LESS THAN "Q "THEN 
	DISPLAY "DELETIONS COMPLETED" 
      GO TO FINISH; 
    ELSE GO TO DELETE-REC; 
    ELSE 
	DISPLAY "CKREAD ERROR, STATUS =", STAT 
    IF STATUS-KEY-1 = "9" THEN 
	CALL "CKERROR" USING STAT, RESULT 
	DISPLAY "CKERROR NO.", RESULT. 
      GO TO READ-REC. 
 
  DELETE-REC. 
    CALL "CKDELETE" USING FILETABLE, STAT. 
    IF STATUS-KEY-1 = "0" THEN 
      DISPLAY "DELETED" 
	GO TO READ-REC; 
    ELSE 
	DISPLAY "CKDELETE ERROR, STATUS = ", STAT 
	IF STATUS-KEY-1 = "9" THEN 
	  CALL "CKERROR" USING STAT, RESULT 
	  DISPLAY"CKERROR NO.=", RESULT 
        GO TO READ-REC. 

In the second example, a file containing the primary keys of those records to be deleted from a KSAM file is read into the working storage area DAT. These key values are used by CKREADBYKEY to locate and read the items to be deleted by CKDELETE.

 
PROCEDURE DIVISION. 
 
START.
  MOVE 2 TO I-O-TYPE, A-MODE. 
  CALL "CKOPEN" USING FILETABLE, STAT. 
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READ-KEY. 
  READ DATA-FILE INTO DAT; 
    AT END GO TO FINISH. 
  CALL "CKREADBYKEY" USING FILETABLE, STAT, REC, NAME OF DAT, KEYLOC, 
RECSIZE. 
  IF STATUS-KEY-1 = "0" THEN 
    GO TO DELETE-RECORD. 
  DISPLAY "CKREADBYKEY ERROR, STATUS = ",STAT. 
  IF STATUS-KEY-1 = "9" THEN 
    CALL "CKERROR" USING STAT, RESULT 
    DISPLAY "CKERROR ", RESULT 
    GO TO READ-KEY. 
DELETE-RECORD. 
  CALL "CKDELETE" USING FILETABLE, STAT. 
  IF STATUS-KEY-1 = "0" THEN 
    DISPLAY REC, " DELETED" 
    GO TO READ-KEY. 
  DISPLAY "CKDELETE ERROR, STATUS =",STAT. 
  IF STATUS-KEY-1 = "9" THEN 
    CALL "CKERROR" USING STAT, RESULT 
    DISPLAY "CKERROR NO. =", RESULT. 
  GO TO READ-KEY. 

	NOTE: If access is shared, the file must be opened with a call to CKOPENSHR. A call to CKLOCK must precede the call to CKREADBYKEY. A call to CKUNLOCK must follow the CKDELETE error tests and should precede the return to READ-KEY.