Device compatibility with previous versions of MFS

If you choose not to define 3270 devices during IMS system definition using the device type symbolic name (option 1), no changes to device format definitions are needed.

If you choose to define 3270 devices during IMS system definition using a device type symbolic name (3270-An) (options 2, 3, and 4), in some cases you must make changes in your 3270 device format definitions.

The examples in the following table include the recommended standard for relating the device type symbolic name to the screen size:

Table 1. MFS device definition compatibility for 3270 devices
Device and Screen Size Device and Screen Size1 New IMS System Definition1
3275 or 3277 (12X40) MFS: DEV TYPE= (3270,1) Model 1 MFS: DEV TYPE= 3270-A5 2,4
3275, 3276, 3277, 3278 (24X80) MFS: DEV TYPE= (3270,2) Model 2 MFS: DEV TYPE= 3270-A2 2,4
3276, 3278 (12X80) MFS: DEV TYPE= (3270,1) Model 1 MFS: DEV TYPE= 3270-A1 2,3
3276, 3278 (32X80) MFS: DEV TYPE= (3270,2) Model 2 MFS: DEV TYPE= 3270-A3 2,3
3276, 3278 (43X80) MFS: DEV TYPE= (3270,2) Model 2 MFS: DEV TYPE= 3270-A4 2,3
3278 (27X132) MFS: DEV TYPE= (3270,2) Model 2 MFS: DEV TYPE= 3270-A7 2,3
Notes:
  1. For screen sizes specified in type or terminal macro.
  2. If the format will be used on the new device and will not be used on the old device, change TYPE= (3270,1) or (3270,2) to 3270-An with the corresponding screen size, and recompile.
  3. See option 3 in the following table.
  4. See option 4 in the following table.

The following table lists the advantages and disadvantages of selecting a specific option for the larger screen device and the required action if you choose to use existing device formats.

Table 2. Advantages and disadvantages of larger screen device
Option Advantage Disadvantage Conversion Action Required
1 You can use existing MFS formats unchanged. You cannot use full screen. No (Use current formats as shown in the previous table.)
2 You can use full screen. You must design new device formats. No (Define new formats.)
3 You can use existing formats as a migration path on the new screen device and you can gradually replace them with new device formats. You must modify existing device formats to use the device symbolic name. Yes (Refer to the previous table.)
4 Consistency in definition for current and new screen sizes. You must modify all formats. Yes (Refer to the previous table.)

IBM 3278-52/3283-52 and IBM 5550 family (as 3270) compatibility

The message format definitions for the IBM® 3278-52/3283-52 are upwardly compatible. However, message formats created with Kanji functions for the 5550 family of devices cannot be used on the IBM 3278-52/3283-52.

Existing 3270 and IBM 5550 family (as 3270) compatibility

Note the following when adding field outlining and input control specifications to existing 3270 and 3278-52/3283-52 message formats:

  • Field outlining
    • For the 3270 display, left line, right line, overline, and underline do not take up a position in the user field. The application program does not have to be modified unless dynamic modification of extended attributes is performed.
    • For the SCS1 printer, MFS reserves print positions for left and right lines. If a field starts from the leftmost column or ends at the rightmost column, the left or right line is not printed correctly because room is not available. To correct this, modify the application program to truncate 1 byte. If two adjacent fields are logically one and the overline and underline should connect, the application program does not have to be modified.

      In either case, for dynamic modification, the application program must be modified.

  • DBCS/EBCDIC mixed fields
    • For 3270 displays, the SO/SI control characters take up 1 byte on the screen. This means that the length on the display is equal to the message format length. Therefore, the existing application program does not have to be changed.

      When assigning DBCS/EBCDIC mixed data to an existing EBCDIC field, the application program must check that the SO and SI are paired, that the EGCS data is of even length, and that neither the SO nor SI is truncated when the MFLD is mapped to the DFLD.

    • For SCS1 printers, MIX/MIXS must be specified when using DBCS/EBCDIC mixed data. In this case, the message length and the length of the output differ and the application program must modify the MFLD according to each field's characteristics.