XPLink uses X8 and X9 mode TCBs

CICS provides support for C and C++ programs compiled with the XPLINK option by using the multiple TCB feature in the CICS Open Transaction Environment (OTE) technology. X8 and X9 mode TCBs are defined to support XPLink tasks in CICS key and USER key. Each instance of an XPLink program uses one X8 or X9 TCB.

CICS support for programs compiled with the XPLINK option requires only that you show in the PROGRAM resource definition that the program is threadsafe. This indication, and the XPLink “signature” in the load module, are the only things required to put the task on an X8 or X9 TCB.

In the selection of a suitable TCB for a particular program, XPLink takes precedence over the existence of the OPENAPI value for the API attribute on the PROGRAM resource definition.