The TCTUA is an optional extension to the terminal control
table entry (TCTTE), each entry specifying whether the extension is
present, and its length.
You specify that you want a TCTUA associated with a terminal by
defining its length on the USERAREALEN attribute of a TYPETERM
resource
definition. This means that the TCTUAs are of fixed length for all
the terminals created using the same TYPETERM definition.
A terminal control table user area (TCTUA) is safe to use in a
dynamic transaction routing environment as a means of passing data
between successive transactions in a pseudoconversational
transaction.
Like the COMMAREA, the TCTUA is always accessible to transactions
initiated at a user terminal, even when the transactions in a
pseudoconversation
are routed to different target regions. This is illustrated in
Figure 1
. Some other general characteristics
of TCTUAs are:
Minimal processor overhead (only one CICS command is needed to
obtain the address).
It is not recoverable.
The length is fixed for the group of terminals associated with
a given TYPETERM definition. It is suitable only for small amounts
of data, the maximum size allowed being 255 bytes.
If the terminal is autoinstalled, the TCTUA lasts as long as the
TCTTE, the retention of which is determined by the
AILDELAY
system initialization parameter.
The TCTTE, and therefore any associated TCTUA, is deleted when the
AILDELAY interval expires after a session between CICS and a
terminal
is ended.
If the terminal is defined to CICS by an explicit terminal
definition, the TCTTE and its associated TCTUA are created when
the
terminal is installed and remain until the next initial or cold start
of CICS.
The TCTUA is available to a dynamic routing environment in the
routing region as well as application programs in the target region.
It can be used store information relating to the dynamic routing of
a transaction. For example, you can use the TCTUA to store the name
of the selected target region to which a transaction is routed.
Figure 1. The use of a TCTUA by a pseudoconversation in
a dynamic routing environment
