The master terminal

The master terminal is the control center of the DB⁄DC environment. The Master Terminal Operator (MTO) must know all the operating aspects of the system and be familiar with the purpose and action of all the IMS commands that are entered.

Some characteristics of the master terminal are:

• It is used to enter commands that start, stop, and restart the system.
• As a logical terminal, it receives system messages.
• The primary control of the network and connecting terminals is performed through the master terminal. It can start and stop communication lines and assign logical terminals to physical terminal destinations.
• The status of the system can be displayed from the master terminal. Such items as the number of transactions to be processed, the number of programs and databases that are active, and the status of communication lines can be requested.
• If a program or database error occurs, commands can be entered from the master terminal to prevent further processing against the affected resource and to prevent input or output activity for terminals. These recovery actions can also apply to a recovery of the entire system after an abnormal termination occurs.
• If an exception condition occurs, the status of the Online Log Data Set (OLDS) can be displayed, and the function of the OLDS can be controlled from the master terminal.

If the master terminal becomes inoperable, the operating system console can be used as a backup. The MTO can either operate the IMS from the system console or assign the master terminal LTERM (logical terminal) to an alternate terminal. Messages continue to be routed to the old master terminal LTERM until the LTERM is assigned to the system console. The address of the system console is LINE 1 PTERM 1. If the system console is used to continue operation, terminal security is identical to that of the master terminal.