Task 9—Updating the terminal control table assembly

Summary: In this task, you will update the terminal control table (TCT) assembly.

This task is optional. To correctly optimize data streams, the Optimizer must determine the 3270 buffer size in effect for each terminal. This information is extracted by the Monitor from the TCT terminal entry (TYPE=TERMINAL). The information, which CICS and the Optimizer use, must accurately reflect the terminal hardware that is installed.

Definitions for Non-SCS printers

Take particular care with non-SCS 3270 printers. IBM control units deviate from the SNA protocol by binding LUTYPE3 printers with the default physical buffer size of the device, 2 KB or 4 KB, instead of the value that is specified in the DEFSCRN value.

Because the Optimizer has no way to detect the actual buffer size of the printer in the host (CICS), the wraparound point cannot be determined. Consequently, the best optimization might not be obtained. To avoid this problem, define the DEFSCRN and the ALTSCRN parameters explicitly. The printer will be bound with the sizes that you specify.

You can display these parameter values by viewing the Fixed Data Stream Trace Environment panel. For more information about this topic, see Using.

BTAM installations

A data stream that is bound to a basic telecommunications access method (BTAM) local terminal is excluded from Input Suppression if the INAREAL operand of DFHTCT TYPE=LINE is too small. The INAREAL value must be large enough to hold the largest possible inbound data stream. To ensure that Input Suppression is performed for BTAM local terminals, you might have to reassemble your TCT to increase the size of your INAREAL operands.

To update the TCT assembly

1. Use the following parameters in the TYPE=TERMINAL macro to define the 3270 buffer size:

   DEFSCRN—defines the default screen size
   ALTSCRN—defines the alternate screen size
   For example, a 3270 model 4 can be defined as DEFSCRN=(24,80) and ALTSCRN=(43,80).

   In the TCT assembly, the following default parameters are true:

   If DEFSCRN is undefined, the value that is associated with the TRMMODL operand is used.
   If TRMMODL is undefined, the terminal type defaults to model 1. This action sets the screen size to (12,40).

2. To change any of these parameters, reassemble the TCT.