DDS for 3270 remote attachment

The 3270 remote attachment feature allows a 3270 Systems Network Architecture (SNA) controller or a 3274 emulating device to be attached to a System i® model. Some applications for the 3270 that use data description specifications (DDS) might require programming changes.

An operator at a 3277, 3278, or 3279 data entry keyboard can use most features and functions as a similarly configured and authorized 5250 workstation. The attached unit has the same capabilities and limitations as any remote 5251, with the following exceptions:

• No display attributes are seen on either a 3278 or a 3279 when the field is defined as a nondisplay field.
• Numeric-only fields that are used for negative numbers act differently on the 3270 than on the 5250. On the 3270, if the operator enters a negative number in the field, the sign occupies the first position of the field followed by the number. This causes the maximum size of the field to decrease by 1 and should be considered when you design the displays and fields.
• Results that cannot be predicted can occur when data is entered in an input field that is involved in a page command, if any lines involved in the page are not of the same type field attributes and location.
• The following DDS keywords are ignored by 3270 support:
  • AUTO (RA) and CHECK (ER)
  • BLINK (cursor blink is controlled by keyboard for 3270)
  • CHRID
  • CHANGE
  • LOWER or CHECK (LC) (lowercase is controlled by turning on the display for 3270)
  • CHECK (RL and RLTB)
  • DSPSIZ (other than 24 x 80)
  • LOCK
  • MSGLOC (set to row 24)
    Note: For display devices configured as a 3278 Model 4, the MSGLOC keyword is set to display messages on row 43.
• The following DDS display attributes are the only ones valid for 3270 Remote Attachment (except for 3277):

  DSPATR

  RI used for 3278 and 3279 CS used for 3278 and 3279 (changed to UL) UL used for 3278 and 3279 BL used for 3278 (determines color on 3279)

• During a write operation to the error line, the Enter key is defined as a Reset key and cannot be mapped to any other function.

  In addition, if a write operation is requested by the user application to display an error message, a read operation should immediately follow the write operation for the remote 3270 display to allow resetting of the error message. A read operation following a write operation of an error message should be used by call applications regardless of the type of target display. If a read operation does not immediately follow the write error message requested by the user application, remote 3270 displays might overlay the error message before it can be read by the user.