CKREADBYKEY

A call to CKREADBYKEY makes available a record identified by key value from a KSAM file.

   CALL "CKREADBYKEY" USING filetable, status, record, key, keyloc, recordsize

Records can be read from a KSAM file in an order determined by key value. This order need not be sequential; in fact, it can be any order you specify. This type of access is used to access individual records in random order by key value.

Parameters

filetable: An 8 halfword record containing the number and name of the file, its input/output type, access mode, and a code indicating whether the previous operation was successful and if so what it was.
status: One halfword (two 8-bit characters) set to a pair of values upon completion of the call to CKREADBYKEY indicating whether the call was successful and if not why not.
record: A record defined in the WORKING-STORAGE SECTION into which the contents of a record located by key value is read.
key: An item whose value is used by CKREADBYKEY to locate the record to be read. Key values in the file identified by filetable are compared to the value of key until the first record with an equal value is found.
keyloc: One halfword integer (S9(4)COMP) set to the starting character position of the key in the KSAM data record (first position is character 1). The keyloc parameter identifies the file key to be compared with key.
recordsize: An integer (S9(4)COMP) containing the length in characters of the record being read; it must be less than or equal to the maximum record length established for the file at creation.

Operation Notes

In order to use the CKREADBYKEY procedure, the file must be opened for either input or input/output. The access mode can be either random or dynamic, but must not be sequential.

Execution of CKREADBYKEY causes the value of key to be compared to the value of the key at location keyloc in the KSAM file data records. When a key is found whose value is identical to that of key, the record pointer is moved to the beginning of that record and the record is read into the location record.

If no record can be found whose key value equals that of key, an invalid key condition is diagnosed and status is set to the value 23.

Successful execution of CKREADBYKEY is indicated by the value 0 in the left byte of status. Unsuccessful execution is indicated by either the invalid key return or by a value of 9 in the left byte of status.

In order to delete records in random or dynamic mode, CKREADBYKEY must be called before executing CKDELETE. It is not required prior to CKREWRITE.

In the following examples, update information is read into the area called DAT in the WORKING-STORAGE SECTION. (Note that in this as in the preceding examples, the WORKING-STORAGE SECTION from Figure A-2 “Representation of KSAMFILE Used in COBOL Examples” continues to be useful.) In the first example, the primary keys of records in KSAMFILE are searched for values matching the value read into NAME in the DAT record; in the second example, an alternate key at location 23 is searched for values matching the value read into PHONE in the DAT record.

Read a record located by its primary key value:

 

DATA DIVISION. 

.

.

.

WORKING-STORAGE SECTION. 

77 KEYLOC PIC S9(4) COMP. 

.

.

.

PROCEDURE DIVISION. 

START. 

.

.

.

  MOVE 2 TO I-O-TYPE, A-MODE.<--- prepare to open for input/output, dynamic access

  CALL "CKOPEN" USING FILETABLE, STAT. 

  IF STATUS-KEY-1 = "9" THEN 

    CALL "CKERROR" USING STAT, RESULT 

    DISPLAY "CKOPEN ERROR NO. ", RESULT. 

  IF STATUS-KEY-1 NOT="O" THEN 

    DISPLAY "CKOPEN FAILED" 

    STOP RUN. 

FIND-RECORD. 

  READ NEW-DATA INTO DAT;<--- read update records 

    AT END GO TO FINISH. 

  MOVE 3 TO KEYLOC. 

  CALL "CKREADBYKEY" USING FILETABLE, STAT, REC, NAME OF DAT, 

    KEYLOC, RECSIZE. 

  IF STAT = "00" THEN 

    DISPLAY "RECORD FOUND", REC 

    GO TO FIND-RECORD. 

  IF STAT = "23" THEN 

    DISPLAY "RECORD NOT FOUND,KEY=", NAME OF DAT 

    GO TO FIND-RECORD. 

  IF STATUS-KEY-1 = "9" THEN 

    CALL "CKERROR" USING STAT, RESULT 

    DISPLAY "ERROR NO. ", RESULT 

  GO TO FIND-RECORD.

To find a record by the value of an alternate key, simply change two statements in the preceding example so that KEYLOC contains the location of the alternate key and the key value for comparison is found in item PHONE OF DAT rather than in NAME OF DAT:

 

   FIND RECORD. 

     READ NEW-DATA INTO DAT; 

       AT END GO TO FINISH. 

     MOVE 23 TO KEYLOC. 

     CALL "CKREADBYKEY" USING FILETABLE, STAT, REC, PHONE OF DAT, 

       KEYLOC, RECSIZE.

CKREADBYKEY

Technical documentation

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Parameters

Operation Notes