The table below shows suggested BIND field values. To maximise throughput, disable pacing and use Exception-response (RQE) whenever possible (the HSM always requests RQE if permitted by the BIND). The HSM does not support sending the Isolated Pacing Response (IPR), so, if primary-to-secondary pacing is required, the HSM must be bound for Definite-Response (RQD) on that half-session to allow the pacing response to be returned.
|
Byte Number |
Hex Value |
Comments |
|
0 |
31 |
The Bind command. |
|
1 |
01 |
Bind type and format. |
|
2 |
03 |
Function management (FM) profile. |
|
3 |
03 |
Transmission services (TS) profile. |
|
4 |
B1 |
PLU can request single or multiple element RQD or RQE chains. |
|
5 |
90 |
SLU can request single or multiple element RQE chains. |
|
6 |
30 |
Selects EBCDIC code, the HSM supports the use of ASCII if bit 4 is set to one (X'38). This is a global setting, and affects all FMD requests that are character coded; the CSI bit in the RH is ignored. |
|
7 |
80 |
Common protocols byte; Half duplex flip-flop (HDX FF), PLU does error recovery, HSM (3274) speaks first, data contention favors HSM (3274). |
|
8 |
00 |
No secondary-to-primary pacing. |
|
9 |
00 |
No primary-to-secondary pacing. |
|
10 |
87 |
Maximum SLU RU size=1024. (Because of buffer constraints, the HSM never sends an RU greater than 996 bytes). If byte 10 is not accepted by the HSM, the bind is rejected with sense code X'0821. |
|
11 |
87 |
Maximum PLU RU size=1024. (Because of buffer constraints, the Host should never send an RU greater than 988 bytes). If byte 11 is not accepted by the HSM, the bind is rejected with sense code X'0821. |
|
12-n |
|
All remaining bytes are ignored by the HSM. |
From HSM Functional Revision 5.03, the SND HSM accept any legal RU size from 256 and 1024 inclusive, on both inbound and outbound LU-LU half-sessions. This allows connection to IBM AS/400 minicomputers which do not allow the RU size to be changed in the Host and which require the RU size to be 256.
Bytes 10 and 11 in the BIND can contain the following values (in hexadecimal):
|
BIND Value |
Maximum RU Size |
|
85 |
256 |
|
95 |
288 |
|
A5 |
320 |
|
B5 |
352 |
|
C5 |
384 |
|
D5 |
416 |
|
E5 |
448 |
|
F5 |
480 |
|
86 |
512 |
|
96 |
576 |
|
A6 |
640 |
|
B6 |
704 |
|
C6 |
768 |
|
D6 |
832 |
|
E6 |
896 |
|
F6 |
960 |
|
87 |
1024 |
Only one HSM command can be sent outbound per chain, and if a command is sent to the HSM in multiple RUs, the RUs must be chained. Chain elements are concatenated in the HSM and the data is not given to the command processor until the LIC element is received.
The internal buffer is limited to 1024 HSM bytes, so no command, regardless of the number of RUs in the chain, can exceed 1023 bytes total. If a command produces a response containing more data than the inbound or SLU "maximum RU size" specified in the Bind, the HSM blocks the reply into multiple RUs. All response RUs resulting from one HSM command are chained together by the HSM.
From HSM Functional Revision 5.03, data is buffered and passed to the SNA communications output buffer in appropriate-size blocks after the HSM command has been completed. Therefore some degradation in system performance occurs (compared with earlier Functional Revisions) when the RU sizes selected in the Bind are less than 1024 bytes. Select the maximum RU size supported in the Host system to reduce the tendency to subdivide long messages in the HSM. This helps to maximise the Host/HSM system transaction throughput.
To maintain system performance, when the RU size is set to 1024 bytes, program the HSM to disable the double buffering required for small RU sizes. When the double buffering is disabled, data is stored directly into the communications output buffer, thus eliminating any performance degradation.
Most Host commands produce only one reply request; this request carries OIC (BC & EC bits set) and CD set. However, the HSM printing commands (i.e., PE, OA, OE and OG) produce two reply requests and the PIN solicitation processing command can produce as many as 52. The HSM chains these multiple replies together with the last in chain (BC not set & EC set) carrying CD.
If data traffic is disabled using SHUTD, any FMD requests sent outbound after the HSM has returned SHUTC are ignored. The appropriate session-level responses are returned, but data is discarded.
The HSM has no provision for supplying character-coded logons; the Host application or VTAM is responsible for starting the LU-LU session.
The HSM ignores FMD requests on the SSCP-LU session; a positive response is returned, but data is discarded.
Normally, the HSM searches for and discards embedded orders in the 3270 data stream in outbound requests. However, to maximise throughput and allow binary data, the HSM has a "transparent" mode. No order stripping is done in transparent mode, and the Host application must ensure that no 3270 orders are sent. The HSM includes the read header in all inbound FMD requests regardless of mode.