The TCT user area (TCTUA) is an optional extension to the terminal control table entry (TCTTE). Each entry in the TCT specifies whether this extension is present and, if so, how long it is (by means of the USERAREALEN attribute of the TYPETERM resource definition used for the terminal). See the CICS® Resource Definition Guide for more information about the TYPETERM resource definition.
The system initialization parameters TCTUALOC and TCTUAKEY specify the location and storage key for all TCTUAs.
TCTUAs have the following characteristics in common with the CWA:
Unlike the CWA, however, the TCTUA for a particular terminal is usually shared only among transactions using that terminal. It is therefore useful for storing small amounts of data of fairly standard length between a series of transactions in a pseudoconversational sequence. Another difference is that it is not necessarily permanently allocated, because the TCTUA only exists while the TCTTE is set up. For non-autoinstall terminals the TCTUA is allocated from system startup; for autoinstall terminals the TCTUA is allocated when the TCTTE is generated.
Using the TCTUA in this way does not require special discipline among using transactions, because data is always read by the transaction following the one that wrote it. However, if you use TCTUAs to store longer-term data (for example, terminal or operator information needed by an entire application), they require the same care as the CWA to ensure that data used in one transaction does not overlay data used in another. You should not exceed the length of the allocated TCTUA, because this produces a storage violation.
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