Previous hop data characteristics

Previous hop data identifies the remote sender of a request to attach a task, and creates a trail to be followed back into the previous system, which enables data gathering and monitoring to continue in the region that sent the request.

Previous hop data is created if a request to attach a task is transmitted by using an IPIC or MRO connection between CICS® TS 4.2 or later regions. The task that is attached as a result of this request has previous hop data created.

As part of an interrelated transaction, if a task issues requests to attach tasks in other CICS TS 4.2 regions, such as when a daisy chain is used, previous hop data is created for the tasks that are attached in the other CICS regions.

Previous hop data is not created for a task that is the point of origin. For information about association data and the point of origin, see Association data.

This figure illustrates previous hop data and an interrelated transaction by using an IPIC connection across regions 1, 2, and 3. — Figure 1. Previous hop data and an interrelated transaction

The value of previous hop data for a task that is started by use of the START command depends on the TERMID option. Previous hop data is not created for a started task that is at a new point of origin.

If the TERMID option is specified, the started task is treated as starting at a point of origin and no previous hop data is created. This is the case whether the TERMID option specifies a local terminal definition or a remote terminal definition.

When the TERMID option specifies a remote terminal definition, the process to schedule the START command might involve a transfer of the command across a number of CICS systems to reach the target CICS system where the terminal specified in the TERMID option is a local terminal definition.

If the TERMID option is not specified, only the previous hop count is created for the started task and the remaining previous hop data is not set. In this case, the started task inherits the value of the previous hop count from the task in the same CICS region that initiated it.

For example, if a START command without the TERMID option is started by a task that is at a point of origin and the started task runs in the same CICS region, the started task inherits a previous hop count of zero. If the START command without the TERMID option is function shipped to another CICS region, the started task inherits a previous hop count from the mirror task.

Previous hop data programming considerations

Previous hop data includes data items that identify the following information:

Another CICS TS 4.2 or later region that requested the current task to be attached.
The task in another CICS TS 4.2 or later region that requested the current task to be attached.
The number of CICS system hops that are taken for all CICS TS 4.2 or later regions to reach the current CICS system. A value of zero is the point-of-origin CICS system.

Previous hop data is not supported when interrelated transactions of a sequence of tasks are run on a number of CICS systems and a previous hop CICS system is a release earlier than CICS TS 4.2. In this case, not all of the previous hop data is set. The previous hop count field is set to one, and no other values in the previous hop data are set.