# CICS HVT Triggers

This section explains CICS HVT triggers that you can choose to use in certain situations.

Consider using the CICS HVT capability of Substation ES if you require any of the following features:

- You expect a high volume of messages or queue records to be sent from CICS regions. The throughput consideration would be around 200 messages per second.
- You require ordered delivery of information.
- Your applications might send more than 32 KB of information. Trigger data can exceed 32 KB.
- You use TIBCO Enterprise Message Service as your transport and require guaranteed message delivery for triggered information.
- The information to be sent can reside in `DFHCOMMAREA`, TSQ, storage, or a container.
- There are two facilities for storing data during the HVT process:
  - Transient Data Queues (TDQ). To use TDQ, your program links to `SXCQWRIT`.
  - Temporary Storage Queues (TSQ). To use TSQ, your program links to `SXCQWTSQ`.

    Both programs use the same input format.

If you are using the Container or TSQ input option for HVT, the process works in an MRO environment (with proper MRO definitions). The storage pointer option does not work in a MRO environment.

Substation ES provides the program `SXCQWTSQ`, which any CICS application can link to. `SXCQWTSQ` creates a new TSQ entry (name) for each link to `SXCQWTSQ`. The TSQ created is limited to one record with a maximum size of 32000. The TSQ normally uses auxiliary storage. Using `TSMODEL` allows you to change the normal operation to `MAIN`.

HVT using TSQ has no recover or backout. Once the link to `SXCQWTSQ` is done the TSQ entry is created and scheduled for delivery to Substation ES. The HVT TSQ request could be sent to the ESB before the business program that links to `SXCQWTSQ` ends. Because Substation ES processes HVT TSQ entries as fast as possible, the entities are not processed in any order.

The previous methods of directly writing to TDQ are still supported, but impose the same restrictions as the previous versions of the product. All future enhancements will be made according to the HVT concept. HVT is a major enhancement to enable Event Driven Architecture (EDA) for High-Volume Trigger processing in CICS.

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