PUNS-related channel programs
During activation of an NCP in a channel-attached communication controller, the SSCP sends a Contact RU to PUNS. PUNS responds by giving control to ISTTSCP4 to schedule one of five channel programs (A–E in Table 1). When the SSCP sends a Discontact RU to PUNS, one of two channel programs (F and G in Table 1) is executed.
| CCW |
Code
(hex) |
Flags |
Notes
|
|
|---|---|---|---|---|
| A. | Sense | 04 | SLI | Determines if the device needs to be loaded. |
| B. | Write XID
No-Op |
61
03 |
SLI,CC
SLI |
This channel program follows A if the device does not need to be loaded. It is followed by either C or D. |
| C. | Write Break
Read XID Read No-Op |
09
62 02 03 |
SLI,CC
SLI,CC SLI,CC SLI |
This channel program follows B if there is no command reject. |
| D. | Restart/Reset
No-Op |
93
03 |
SLI,CC
SLI |
Executed only if the Write XID in B caused a command reject (implies the NCP is NCP Release 2 or earlier). |
| E. | Contact
Restart/Reset No-Op |
C3® 93 03
|
SLI,CC
SLI,CC SLI |
Restart/Reset is executed only if a Contacted (error) response is sent to PUNS. |
| F. | Discontact
No-Op |
A3
03 |
SLI,CC
SLI |
This channel program is executed only if B did not cause a command reject. |
| G. | No-Op | 03 | SLI | This channel program is executed if B caused a command reject. |
These CCWs are contained in I/O buffers that are allocated from the IOBUF buffer pool when doing PUNS I/O.
The data area pointed to by the address portion of a Read XID or Write XID CCW is described in ISTXID in z/OS® Communications Server: SNA Data Areas Volume 1.