Execute Channel Program (EXCP) Section

For each device assigned to each non-spooled data set, there is an eight-byte entry with the following format:

Offsets Name Length Format Description
0 0 TIVEXCP 8 Structure Data set access information.
Note: Virtual I/O devices are identified by the following:
Device Class
0
Unit Type
0
Device Number
X'7FFF'
It is important to understand the following:
  • Allocation messages for VIO data sets will show VIO ALLOCATED TO ddname.
  • SMF records will show VIO unit addresses as X'7FFF'.
  • The actual in-storage UCB built for VIO will show address X'3FFF'.
For example, the messages:
  • IEF237I X'3FFF' ALLOCATED TO ddname
  • IEF237I X'7FFF' ALLOCATED TO ddname
indicate that ddname is not allocated to a Virtual I/O device, but is instead allocated to a real device whose unit address is X'3FFF' or X'7FFF' respectively.
0 0 TIVDEVC 1 binary Device class.
1 1 TIVUTYP 1 binary Unit type.
2 2 TIVCUAD 2 binary Device number.
4 4 TIVNEXCP 4 binary Execute channel program (EXCP) count. See offset 102 — TIVRIN.
Parent topic: Record Mapping