The CNM headers, shown in Table 1 and Table 2, allow a standard method of routing replies
to requesting application programs; this routing is based on PRID
correlation. The header format also allows a standard correlation
scheme for the application program. When an NS RU, embedded in a Deliver
request, contains a standard CNM header, a CNM header bit is set in
the flag field of the Deliver RU that is sent to the application program.
When an NS RU, embedded in a Forward request, follows the standard
format and has reply data associated with it, the application program
can set the reply-requested field of the Forward request to receive
the requested reply data. Failure to set this flag causes reply data
to be treated as unsolicited data by the SSCP and to be routed to
the application program assigned to receive such an unsolicited NS
RU. For details on the routing table, refer to z/OS Communications Server: SNA Customization.
Table 1. Standard CNM header,
SSCP-PU request format| Byte |
Bit |
Value |
Description |
|---|
| 0–2 |
|
|
Network service header |
| 3–7 |
|
|
CNM Header is bytes 3–7 |
| 3–4 |
|
|
CNM target ID; refer to CNM target
ID descriptor field in byte 5 |
| 5–6 |
0–1 |
|
Reserved |
| |
2–3 |
|
CNM target ID descriptor |
| |
|
B‘01’ |
Network address of target resource
is in bytes 3 and 4 |
| |
|
B‘00’ |
Local address of target resource
is in byte 4; byte 3 is reserved |
| |
4–15 |
|
PRID |
| 7 |
0 |
|
Limited usage (See the following
note) |
| |
1 |
|
Reserved |
| |
2–7 |
|
Type, specifies the format of request-specific
data when present in bytes 8–n |
| Note: Bit
0 in byte 7 is used as a set/reset indicator in certain requests,
for example, REQMS. Specific requests can use this bit where required.
Whenever a central data base is used, requests to reset counters recorded
by the data base must come only from the application program that
updates the data base with the reset information; otherwise, the data
base contains misleading information.
|
Table 2. Standard CNM header,
PU-SSCP request format| Byte |
Bit |
Value |
Description |
|---|
| 0–2 |
|
|
Network service header |
| 3–7 |
|
|
CNM header is bytes 3–7 |
| 3–4 |
|
|
CNM target ID; refer to CNM target ID descriptor field in byte
5 |
| 5–6 |
0–1 |
|
Reserved |
| |
2–3 |
|
CNM target ID descriptor |
| |
|
B‘01’ |
Network address of target resource is in bytes 3–4. Network
address information should not be used by application programs, because
this network-specific data is subject to change. |
| |
|
B‘00’ |
Local address of target resource is in byte 4; byte 3 is reserved |
| |
4–15 |
|
PRID |
| 7 |
0–1 |
|
Reply Flags: |
| |
0 |
|
Solicitation Indicator Reply Flag |
| |
|
B‘0’ |
Unsolicited request |
| |
|
B‘1’ |
Solicited (reply) request |
| |
1 |
|
Not-Last-Request Indicator |
| |
|
B‘0’ |
No more data (for example, last reply) |
| |
|
B‘1’ |
More data (for example, not-last reply) |
| |
2–7 |
|
Type (Specifies the format of the data in bytes 8–n) |
z/OS Communications Server: SNA Programming
Copyright IBM Corporation 1990, 2014