Design requirements

Follow these procedures when writing this routine:

Use standard linkage.
Save and restore registers 2–14.

Consider the following restrictions when writing this routine:

The name of the command verification exit routine module should be ISTCMMND; however, if you have written an alternate load module, use the load module name you assigned to your replacement module.
Do not issue any SVCs if this exit routine is running in SRB mode.
This exit routine should use only conditional storage invocations. You can reduce the possibility of a VTAM® abend during a storage shortage by coding conditional storage invocations.
This exit routine is addressable in 31-bit mode only. Data is always presented with 31-bit addressability.
This exit routine can be above or below the 16M line.
This exit routine must be link-edited into the appropriate library. See Installing VTAM exit routines for more information.
This exit routine operates as an internal VTAM routine. VTAM performance might be degraded if the routine requires lengthy processing time. While this exit routine has control, VTAM does not process any new VTAM operator requests, session initiation requests, or session termination requests for any resource.
A program check causes VTAM to abend.
System waits, including implied waits for I/O operations, should be avoided. System waits can cause VTAM failure in some timing-dependent situations.
This exit routine operates enabled in pageable storage. The routine gets control in supervisor state with a VTAM storage key. Errors in the routine could damage VTAM or system control blocks and modules.
If VTAM calls the exit for processing, VTAM passes the addresses of the command string and the command string length field to the exit when the operator enters the command. Do not alter any storage area beyond the end of the string or attempt to add characters to the command string. This type of processing could damage VTAM or system control blocks and modules.