IBM SC33-1683-02 - Manual (Page 266)

VTAM terminal management program exit XZCATT
Exit XZCATT
When invoked
Before task attach for terminal tasks.
Exit-specific parameters
UEPTCTTE
Address of the terminal control table terminal entry (TCTTE). The
TCTTE can be mapped using the DSECT DFHTCTTE.
UEPTIOA
Address of the terminal input/output area (TIOA). The TIOA can be
mapped using the DSECT DFHTIOA. However, fields TIOASAL and
TIOASCA are not programming interfaces.
UEPTPN
Address of the APPC transaction process name (TPN), or the
LU6.1 process name (DPN), whose length is addressed by the
parameter UEPTPNL.
UEPTPNL
Address of a 1-byte field containing the length of the TPN or DPN.
UEPTRAN
Address of the 4-byte transaction ID.
Note: The exit program must not change the TRANSID of tasks
started by automatic transaction initiation (ATI). (This is
because CICS needs to match the TRANSID in its program
control table with the TRANSID in the automatic initiate
descriptor (AID) that was created in the AOR.)
Return codes
UERCNORM
Continue processing.
XPI calls
All can be used.
VTAM terminal management program exit
234 CICS TS for OS/390: CICS Customization Guide