Design requirements

Follow these procedures when writing this routine:

Consider the following restrictions when writing this routine:

The name of the virtual route pacing window size calculation exit routine module must be ISTPUCWC.
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.
All data is addressable in 24-bit mode only.
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 subroutine. VTAM performance might be degraded if the routine requires lengthy processing time. While this routine has control, VTAM does not process any new operator requests, session initiation requests, or session termination requests for any resource.
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 gains control in supervisor state with a VTAM storage key. Errors within the routine could damage VTAM or system control blocks and modules.