Generation of I-O Formats

When all field descriptions are identical, and you have requested INPUT or OUTPUT fields implicitly or explicitly, only one set of field descriptions is generated. This type of description is annotated with a comment line reading, “I-O FORMAT: format-name”. Neither -I nor -O is appended to the record format name.
Note: This always happens for database files because all field descriptions within a database file are identical.(See Figure 1.)
Figure 1. Generation of I-O Formats
5722WDS V5R4M0  060210 LN  IBM ILE COBOL         TESTLIB/STRTEXTD     I-SERIES1  06/02/15 11:27:50     Page  2
                                    S o u r c e
STMT PL SEQNBR -A 1 B..+....2....+....3....+....4....+....5....+....6....+....7..IDENTFCN S COPYNAME   CHG DATE
  1     000100 IDENTIFICATION DIVISION.
  2     000200 PROGRAM-ID. STRTEXTD.
        000300
  3     000400 ENVIRONMENT DIVISION.
  4     000500 CONFIGURATION SECTION.
  5     000600   SOURCE-COMPUTER. IBM-ISERIES.                                                       02/02/21
  6     000700   OBJECT-COMPUTER. IBM-ISERIES.                                                       02/02/21
  7     000800 INPUT-OUTPUT SECTION.                                                                 02/02/21
  8     000900 FILE-CONTROL.
  9     001000     SELECT FILE-1 ASSIGN TO DATABASE-NAMES
 11     001100     ACCESS IS DYNAMIC RECORD KEY IS EXTERNALLY-DESCRIBED-KEY
 13     001200     ORGANIZATION IS INDEXED.
        001300
 14     001400 DATA DIVISION.
 15     001500 FILE SECTION.
 16     001600 FD  FILE-1.
 17     001700 01  RECORD-DESCRIPTION.                                                               02/02/21
        001800     COPY DDS-RDE OF NAMES.                                                            02/02/21
       +000001*    I-O FORMAT:RDE        FROM FILE NAMES      OF LIBRARY TESTLIB            RDE
       +000002*                          RECORD DESCRIPTION                                 RDE
       +000003*THE KEY DEFINITIONS FOR RECORD FORMAT  RDE                                   RDE
       +000004*  NUMBER               NAME                RETRIEVAL       ALTSEQ            RDE
       +000005*   0001   LNAME                            ASCENDING         NO              RDE
       +000006*   0002   FNAME                            ASCENDING         NO              RDE
       +000007*   0003   MINAME                           ASCENDING         NO              RDE
       +000008*   0004   MNAME                            ASCENDING         NO              RDE
 18    +000009       05  RDE.                                                               RDE
 19    +000010           06 FNAME                 PIC X(20).                                RDE
       +000011*                  FIRST NAME                                                 RDE
 20    +000012           06 MINAME                PIC X(1).                                 RDE
       +000013*                  MIDDLE INITIAL NAME                                        RDE
 21    +000014           06 MNAME                 PIC X(19).                                RDE
       +000015*                  REST OF MIDDLE NAME                                        RDE
 22    +000016           06 LNAME                 PIC X(20).                                RDE
       +000017*                  LAST NAME                                                  RDE
 23    +000018           06 PHONE                 PIC S9(10)      COMP-3.                   RDE
       +000019*                  PHONE NUMBER                                               RDE
 24    +000020           06 DATA-DDS              PIC X(40).                                RDE
       +000021*                  REST OF DATA                                               RDE
 25     001900 66  MIDDLE-NAME RENAMES MINAME THRU MNAME.
        002000
 26     002100 PROCEDURE DIVISION.
        002200 MAIN-PROGRAM SECTION.
        002300 MAINLINE.
 27     002400     OPEN INPUT FILE-1.
        002500*      .
        002600*      .
        002700*      .