Problems Reading Indexed File (COBOL)

I have a huge problem in a program revolving around reading an indexed file. While the program involves two other reads that work just fine this one keeps giving me problems. Here is the code for everything that involves it:

       SELECT PO-MASTER-FILE
           ASSIGN TO 'PO-INDEXED.DAT'
           ORGANIZATION IS INDEXED
           ACCESS IS RANDOM
           RECORD KEY IS PO-KEY
           FILE STATUS IS FILE-STATUS-CODE.

   DATA DIVISION.
   FILE SECTION.

   FD  PO-MASTER-FILE.
   01  PO-MASTER-RECORD.
       05  PO-KEY.
           10  PO-VEND-NUMBER-M        PIC X(4).
           10  PO-ORDER-ID-M           PIC X(8).

   WORKING-STORAGE SECTION.
       05  PO-KEY-S.
           10  POLI-VEND-NUMBER-S      PIC X(4).
           10  POLI-ORDER-ID-S         PIC X(8).

   SCREEN SECTION.
       05  LINE 07  COLUMN 23  VALUE 'NUMBER:'
               FOREGROUND-COLOR 10.
       05  LINE 07  COLUMN 50          PIC X(4)
               USING POLI-VEND-NUMBER-S
               FOREGROUND-COLOR 15 AUTO.
       05  LINE 08  COLUMN 23  VALUE 'ORDER ID:'
               FOREGROUND-COLOR 10.
       05  LINE 08  COLUMN 50          PIC X(8)
               USING POLI-ORDER-ID-S
               FOREGROUND-COLOR 15 AUTO.

   PROCEDURE DIVISION.
   100-MAIN.
       OPEN I-O   POLI-MASTER-FILE
                  PO-MASTER-FILE
                  ITEM-MASTER-FILE

       PERFORM 120-DISPLAY-SCREEN
           UNTIL FUNCTION-CODE-S = 'END' OR 'end'

           CLOSE  POLI-MASTER-FILE
                  PO-MASTER-FILE
                  ITEM-MASTER-FILE

           EXIT PROGRAM
           STOP RUN.

   120-DISPLAY-SCREEN.

  ****
       MOVE FUNCTION-CODE-S TO SAVE-FUNCTION-CODE

  ****
       MOVE POLI-VEND-NUMBER-S TO SAVE-VEND-NUMBER

  ****
       CALL 'DATETIME' USING DATE-TIME-PASS-AREA

       DISPLAY SCREEN-IMAGE
       ACCEPT SCREEN-IMAGE

       IF FUNCTION-CODE-S = 'END' OR 'end'
           CONTINUE
       ELSE
           PERFORM 200-PROCESS
       END-IF.

   200-PROCESS.
       MOVE SPACES TO ERROR-MESSAGE-S
       EVALUATE TRUE
           WHEN FUNCTION-CODE-S = 'INQ' OR 'inq'
               PERFORM 300-INQUIRY
           WHEN FUNCTION-CODE-S = 'ADD' OR 'add'
               PERFORM 400-ADD
           WHEN FUNCTION-CODE-S = 'CHG' OR 'chg'
               PERFORM 500-CHANGE
           WHEN FUNCTION-CODE-S = 'DEL' OR 'del'
               PERFORM 600-DELETE
           WHEN OTHER
               MOVE 'Invalid Function Code' TO ERROR-MESSAGE-S
       END-EVALUATE.

   400-ADD.
  ****
       PERFORM 900-VALIDATE-THE-FIELDS THRU 999-EXIT
       IF ERROR-MESSAGE-S = SPACES
           PERFORM 420-OK-TO-ADD-THE-RECORD
       ELSE
  ****
           MOVE SPACES TO POLI-DATE-ADDED-S
       END-IF.

   900-VALIDATE-THE-FIELDS.
       MOVE PO-KEY-S TO PO-KEY
       READ PO-MASTER-FILE
           INVALID KEY
               IF FILE-STATUS-CODE = '23'
        开发者_如何学JAVA           MOVE 'Vendor Number Or Order ID Is Not Found'
                       TO ERROR-MESSAGE-S
                   GO TO 999-EXIT
               ELSE
                   MOVE FILE-STATUS-CODE TO UNEXPECTED-CODE
                   MOVE UNEXPECTED-CODE TO ERROR-MESSAGE-S
               END-IF
       END-READ

There is more validation code after this point and the program skips right over this part as if it finds a file even if I leave POLI-VEND-NUMBER-S and POLI-ORDER-ID-S blank on the screen. I am a bit stumped to say the least. Any help will be appreciated. Thank you for your time.

---

Ok, I figured out the problem. It seems that I left out some fields that were in the indexed file because they were not needed in this part of the program. As a result the record would not load and (For some reason) the read was skipped. Basically this is what was missing:

   FD  PO-MASTER-FILE.
   01  PO-MASTER-RECORD.
       05  PO-KEY.
           10  PO-VEND-NUMBER-M        PIC X(4).
           10  PO-ORDER-ID-M           PIC X(8).
       05  PO-DATE-ADDED-M.
               10 PO-DA-YEAR-M         PIC X(4).
               10 PO-DA-MONTH-M        PIC XX.
               10 PO-DA-DAY-M          PIC XX.

Thanks to anyone who looked at this and tried to help.