3270 terminal components that operate with IMS
You must understand the various functions of 3270 terminal to work with IMS.
Terminal display size
The 3270 display station can display from 480 to 3564 characters of information, depending on the model. These characters can be alphanumeric characters, special characters, certain device-control characters (visible on the screen), and attribute bytes (not visible on the screen). In addition, you can prevent display of information in certain fields on the screen.
3270 terminal page-advance function
A transaction's output can be more than one full screen of data. You request the additional output by pressing the PA1 (program access 1) key on the terminal keyboard. If you continue to press the PA1 key, the terminal displays successive pages until you reach the end of the current message. If you press PA1 when there are no more messages waiting to be sent to the display station, the display remains unchanged or IMS sends an appropriate error message.
3270 terminal message-advance function
If you press the PA2 key at any time during a message, IMS deletes the current output message and displays the next message. If no messages are waiting when you press the PA2 key, IMS does not modify the screen.
How to enter passwords from 3270 through MFS
Entering a password through Message Format Service (MFS) can be different from password entry on a cleared screen or on other IMS terminals.
Terminal operator logical paging
If you do not specify operator logical paging, the terminal operator can advance pages only one at a time, by using the page advance function. If you do specify operator logical paging in the application program's message output description, the terminal operator can page forward or backward to any page in a message.
Modified data tags and the 3270 keyboard
IMS resets modified data tags each time it unlocks the 3270 keyboard.
3270 terminal screen protection
Under certain conditions, IMS avoids sending output to a 3270 terminal that could possibly destroy the operator's current work. IMS protects the screen so that you can safely enter data or control requests.
3270 terminal lock and unlock option
During IMS system definition, by using the TERMINAL and TYPE macros or Extended Terminal Option (ETO) logon descriptors, you can specify whether the application program or IMS should be responsible for unlocking the terminal keyboard and resetting the modified data tags.
3270 MFS bypass option
If you select the 3270 Message Format Service (MFS) bypass option (by using a MOD name of DFS.EDTN), the application program controls the functions performed by the Clear key, selector pen attention, PA1, PA2, or PA3 keys.
3270 MFS protected field validation
Set MFSPFV=Y in the DFSDCxxx member of the IMS PROCLIB data set to configure the 3270 MFS protected field validation option, which verifies whether the content of a protected field from the input is different from the original content sent out to the 3270 device.
3270 terminal programmed symbols
Programmed symbols (PSs), an optional feature of the 3270 terminal, allow storage and access of up to six sets of 190 characters, each of which can be user-defined and loaded by the program. You can load PS buffers with either a VTAM® application or a user-defined procedure. After the PS buffers are loaded, you can use them on a field-by-field basis on the screens formatted by the Message Format Service (MFS).
3270 terminal screen formats
The 3270 can operate with either an unformatted or a formatted screen. Additionally, there are also input formats supplied by IMS, and installation-defined formats.
Multiple physical page input
An input message can consist of more than one physical page. For example, a 3275 or 3277 Model 1 display (480 characters) requires four physical pages for an input message designed to be equal to the 3275 or 3277 Model 2 screen size (1920 characters).
3270 master terminal support
A 3270 terminal can be the IMS master terminal. When the IMS master terminal is a 3270 terminal, IMS sends all system messages to the primary device. IMS also sends selected system-generated messages critical to IMS operation to the secondary device.
3270 terminal copy function
You can use the IMS Copy function to obtain a printed copy of the currently displayed screen on a remote terminal. You can define the Copy function for one or more terminals on a remote 3270 line.
3270 terminal function keys
Certain keys on the display station keyboard are reserved for use by IMS. If you press any of these keys (or the selector light pen or operator ID reader) when the terminal is not screen protected, IMS might not be able to recognize your action.
3284 Model 3 printer operation
When attached to a 3275 terminal, IMS supports the 3284-3 printer as a component of the 3275 terminal. IMS considers the display portion of the terminal to be component 1 (COMPT 1) and the printer portion to be component 2 (COMPT 2).
Parent topic:
3270 Information Display System