HP 3000 Manuals

HP COBOL II/XL Reference Manual

DELETE Statement 

The DELETE statement logically removes a record from a relative or
indexed file.

Syntax 


            

Parameters 

file-name-1             the name of the file from which the record is to
                        be deleted.  The file must be an indexed or
                        relative file opened in input-output mode.

imperative-statement-1  one or more imperative statements.
and
imperative-statement-2 

Description 

If the specified file is being used in sequential access mode, the
INVALID KEY or  NOT INVALID KEY phrase must not be specified.  However,
if the file is being used in any other access mode and there is no
applicable USE procedure, these clauses must be specified.[REV BEG] For
information on handling I/O errors, see "Input-Output Error Handling
Procedures" .[REV END]

After a successful execution of a DELETE statement, the selected record
has been logically removed from the file, and can no longer be accessed.


NOTE  "Logically removed" means that the record has been marked for
      deletion, and not physically removed.  The contents of the record
      area associated with the specified file are unaffected.  The file
      position indicator is also unaffected.


The execution of the DELETE statement causes the value of the FILE STATUS
data item, if specified for the file, to be updated.  Refer to "FILE
STATUS Clause" in Chapter 6  for valid status keys. 

Selection of the record to be deleted is accomplished in one of two ways,
depending upon what access mode is specified for the file.

For files being used in sequential access mode, the record to be deleted
is the last record read by a successfully executed READ statement.  The
READ statement must be the last input-output operation performed on the
file prior to execution of the DELETE statement.

For files in dynamic or random access mode, the record removed is that
record identified by the contents of the RELATIVE KEY or RECORD KEY data
item associated with the specified file.  If the file does not contain
the record specified by the key, an INVALID KEY condition exists.

If the INVALID KEY phrase has been specified, and the execution of a
DELETE statement causes an INVALID KEY condition, the imperative
statements specified in the INVALID KEY phrase are executed.  Any USE
procedure specified for the file is ignored. 

When no INVALID KEY condition exists, control is transferred to the end
of the DELETE statement  or to the imperative statement specified in the  
NOT INVALID KEY phrase, if specified.[REV BEG] For more information on
handling I/O errors, see "Input-Output Error Handling Procedures"
.[REV END]

For indexed files, if the primary record key has duplicates specified for
it, you should use the DELETE statement only when the file is open in
sequential access mode.  This is because a DELETE statement for such
files open in dynamic or random access mode deletes the first record
written to the file that has the same primary key value as the value
placed in the RECORD KEY data item.  This first occurrence of the
duplicate value may not be the record you want to delete.

Example 

The following example shows the DELETE statement:

            :
     ENVIRONMENT DIVISION.
     INPUT-OUTPUT SECTION.
     FILE-CONTROL.
     SELECT REL-FILE
         ASSIGN TO "DATAFL1"
           ORGANIZATION IS RELATIVE
           ACCESS MODE IS SEQUENTIAL
           FILE STATUS IS CHK-REL-FILE.
     SELECT INDX-FILE
         ASSIGN TO "DATAFL2"
           ORGANIZATION IS INDEXED
           ACCESS MODE IS RANDOM
           RECORD KEY IS KEY-DATA
           FILE STATUS IS CHK-INDX-FILE.
     DATA DIVISION.
     FILE SECTION.
     FD REL-FILE.
     01 REL-DATA
        02  DATA-1                     PIC 99.
     FD INDX-FILE.
     01 INDX-DATA.
        02 KEY-DATA                    PIC X(5).

     PROCEDURE DIVISION.
            :
         OPEN I-O REL-FILE  INDX-FILE.
         READ REL-FILE RECORD  AT END STOP RUN.
         IF DATA-1 IS EQUAL TO 0 THEN DELETE REL-FILE RECORD.
            :
         MOVE "MEYER" TO KEY-DATA.
         DELETE INDX-FILE RECORD
             INVALID KEY PERFORM CHECK-OUT.
            :
     CHECK-OUT.
         DISPLAY "VALUE OF CHK-INDX-FILE IS"  CHK-INDX-FILE.
         DISPLAY "WHAT ACTION TO BE TAKEN?".
         ACCEPT ACTION-ITEM.

MPE/iX 5.0 Documentation