How to use TCO to complete different tasks

IMS loads and processes time-controlled operations (TCO) scripts and exit routines in the IMS control region. So, you can modify either the script or the TCO exit routine without stopping and restarting IMS or disrupting operations.

TCO operates by processing a script that is an unblocked 80-character member in a partitioned data set. The script contains time schedule requests and, optionally, messages that are passed to the TCO exit routine.

At the time specified in a time schedule request, IMS loads a TCO exit routine and schedules it to perform a task. If the TCO exit routine generates input, IMS passes this input to the TCO device dependent module, which then passes the data to IMS using standard DL/I interfaces. If the data is a command, IMS executes it. If it is a transaction or a message switch, IMS enqueues it for processing.

IMS displays output generated from the input, including commands, on any non-ETO device you specify. Thus, you can log all input and output for automatically-generated commands or other activity.

Automatically starting IMS resources

After IMS starts, TCO can execute any non-restart commands. It can start message regions and telecommunication lines, and automatically display the system status.

Peak load handling

The TCO exit routine can assign extra message regions or terminate message regions that you no longer need based on the time of day or the status of the IMS message queues.

Start non-IMS jobs

TCO can start non-IMS-related jobs at a specific time by issuing the /START REGION procname command. For example, you can specify that:

  • At 8:00 p.m., TCO notifies users that an application will terminate.
  • At 8:15 p.m., TCO stops transactions for the application.
  • At 8:16 p.m., TCO starts the non-IMS job.

Schedule low-priority jobs

You might have some types of transactions that are processed only once or twice a day, usually by BMPs. By collecting these transactions in the message queues at 0 priority, TCO can schedule and process the transactions at less busy times. For example, assuming your operators leave for lunch at 12:00 p.m., you can specify that:

  • At 12:05 p.m., TCO issues an /ASSIGN command to reassign the transactions' priority (greater than 0), so processing can begin. If a the transactions need a BMP, TCO can generate one using the /START REGION command.
  • At 12:50 p.m., TCO reassigns the transactions' priority to 0.

By the time the operators return from lunch, processing can continue for high-priority jobs.

Handle multiple time zones

If some of your IMS systems are in one time zone, for example United States Eastern-standard time, and other systems are in another time zone, for example United States Pacific time, the TCO exit routine can automatically start and stop terminals and other resources, taking the time difference into account.

System monitoring

TCO can automatically maintain periodic displays of the pools, message queues, and system status without operator intervention.

Update user status

You can automatically update the status or location of user terminals on a regular basis.

Start large networks in phases

TCO can start a large teleprocessing network in phases to prevent IMS, VTAM®, or NCP resource overloads. By issuing a command for a few nodes on each physical line rather than all nodes on a few physical lines, the network starts more quickly because of increased parallel activity.

Starting large networks in phases example

While IMS is starting, TCO can issue an /OPNDST command to start 100 nodes. A minute later, TCO can issue another /OPNDST command to start another 100 nodes. Two minutes after startup, TCO can start another 100 nodes, and so on, until the entire network is started.

Shut down IMS

The TCO exit routine can notify users that IMS will shut down, and, for example, 10 minutes later, it can stop the telecommunication lines and message regions. TCO can even issue the /CHECKPOINT command to shut IMS down.