The HCON Adapters and Protocols figure shows the protocols and session types supported for each type of HCON connectivity. The control unit prerequisites are identified by lowercase letters a through d.
The HCON SNA function is dependent on the connectivity type and the source of SNA support. SNA support can be from the SNA Services program or from within HCON. See "SNA Support".
The 3174/3274 attachment uses the 3270 Connection Adapter. The Distributed Function Terminal (DFT) protocol gives the HCON program the ability to attach to a 3174 or 3274 controller configured to operate in pass-through mode.
When the local system connects to the host, using a controller and DFT connection over a coaxial cable, the 3174 or 3274 control unit handles the remote and channel protocol. However, the LU (for SNA sessions) and 3270 (for all DFT sessions) data stream processing is done locally by the e789lus and e789x or xhconx emulator processes, respectively.
Each 3270 coaxial connection can support up to five sessions. The supported session types include:
| Protocol | Session Type |
| Non-SNA | Display and host-addressable printer |
| SNA | Display |
HCON supports these DFT capabilities:
Note: This option is required from the controller if non-SNA printing is desired.
HCON does not support the following DFT capabilities:
When HCON connects using the DFT protocol, it adjusts to the attachment protocol (either SNA or non-SNA) of the 3174/3274 or an equivalent controller. You do not have to specify in the configuration which protocol to use.
The SNA DFT Network figure shows an SNA information network. With this configuration, the System Service Control Point (SSCP) session allows the user to choose the data host. The 3X74 controller is attached to System B using an SNA channel.
Attachments to a 5088, 5088-11R, or 6098 Graphics Control Unit are made using a Host Interface Adapter (HIA). The graphics controller can be remote or local. The controller connects to a mainframe host in a non-SNA environment. This type of attachment allows session functional capabilities equivalent to those of other display sessions.
The DFT, HIA, and TCP/IP Connections to Separate Hosts figure shows three distinct data hosts. Each host has different 3X74 controller-protocol requirements, Host A. Host B uses a 5088 Graphics Controller Unit. Host C uses a 3172 Interconnect Controller. In that configuration, each connection requires a 3270 Connection Adapter with up to five logical sessions from each connection. The 5088 controller requires an HIA connection. The TCP/IP attachment requires at least one of the existing local system LAN adapters.
Attachments to a 3172 or 8232 Interconnect Controller are made using these adapters:
The control unit is locally attached to the mainframe host. The LANs supported are IEEE 802.5 (Token-Ring), FDDI, and IEEE 802.3 (CSMA/CD), which includes the Ethernet V2.0. Multiple display sessions can be activated between the host and the local system.
Direct attachment to S/370 or S/390 mainframe hosts can be made using:
Note: TCP/IP protocol is supported for a direct attachment. TCP/IP is required on VM or MVS. HCON uses the Telnet 3270 option.
The direct channel attachment enables the local system to serve as a gateway between a LAN and a mainframe host. The Gateway Configuration between Mainframe Hosts and Multiple LANs figure shows this type of relationship between multiple LANs and mainframe hosts.
HCON in the SNA standalone mode requires that SNA Services be installed on the local system. Before HCON can be invoked, SNA Services must be active and the appropriate adapter must be installed. Only logical unit (LU) types 1, 2, and 3 are supported.
The standalone SNA attachment connects to a mainframe host using these connection types and adapters:
Each SNA node from the local system, whether connecting to the same or a different host, requires a separate connection. Each connection can coexist with and operate independently of the other connections.
The local system in SNA Standalone mode emulates a SNA Type 2.1 node with dependent LUs. The system supports LU types 1, 2, and 3 concurrently, with a limitation of 253 LUs per node. However, the actual performance and response time of each LU depends on the system workload and type of application.
The implementation of SNA sessions emulates an SNA Node T2.1. The node implementation is within the local system using SNA Services. Communication takes place between network addressable units (NAUs) using the logical connection as a session. In a networked environment, the host always contains the primary LU (PLU) and the System Service Control Point (SSCP). The local system contains the secondary LU (SLU). Each SLU works independently of all the others, while working with its partner PLU or the SSCP in the host.
Once a session (SSCP to SLU or PLU to SLU) is established between NAUs, data and control information is exchanged. The SSCP to SLU session enables the SLU to request SSCP assistance to initiate PLU to SLU sessions. This enables the two applications to be in session. For example, the host application and the terminal user can communicate interactively. The standalone PLU to SLU session types are:
Several layers handle SNA standalone session processing:
The SNA Standalone Structure figure shows the structure of layers in standalone mode.
The SNA Standalone Attachments figure shows an SNA information network. In the configuration shown, the SSCP session allows the user to select the data host. A dial-up or leased line through a telephone company is used to provide access to System B, while a Token-Ring connection is used to connect another system to System C. Both users can access all the systems within the company's information network.
SNA support can be from the SNA Services program or from within HCON. HCON SNA function is dependent on the connectivity type and the source of SNA support.
This table lists the SNA commands supported by a local system under SNA DFT or standalone mode.
| SNA Commands Supported | ||||||||
| Name | Type | SSCP ---> | Node <--- | SSCP ---> | SLU <--- | PLU ---> | SLU <--- | |
| ACTPU | SC | 1,2 | ||||||
| DACTPU | SC | 1,2 | ||||||
| ACTLU | SC | 1,2,3 | ||||||
| DACTLU | SC | 1,2,3 | ||||||
| BIND | SC | 2,3 | ||||||
| UNBIND | SC | 2,3 | 1,2 | |||||
| SDT | SC | 2 | ||||||
| CLEAR | SC | 2,3 | ||||||
| CANCEL | DFC | 2,3 | ||||||
| BID | DFC | 2,3 | ||||||
| CHASE | DFC | 2,3 | ||||||
| SIGNAL | DFC | 2,3 | ||||||
| SHUTD | DFC | 2,3 | ||||||
| RSHUTD | DFC | 2,3 | ||||||
| SHUTC | DFC | 2,3 | ||||||
| LUSTAT | DFC | 2,3 | ||||||
| RTR | DFC | 3 | ||||||
| Data | FMD | 3 | 3 | 3 | 3 | |||
| Notify | FMD | 1,2 | ||||||
| REQMS | FMD | 1 | ||||||
| RECFMS | FMD | 1 | ||||||
| NMVT (Alert) | FMD | 1 | ||||||
| NMVT (RTM) | FMD | 1 | 1 | |||||
| NVMT (RSID) | FMD | 1 | 1 | |||||
| Notes: 1 = Processed/generated by 3X74 controller. 2 = Processed/generated by SNA Services 3 = Processed/generated by HCON SNA. | ||||||||
If you run a large number of HCON sessions concurrently, your system can require tuning to avoid processor or memory utilization difficulties. For each invocation of the e789x command, 400KB of system paging space is required. Sufficient disk paging space can be configured on your system to support the maximum allowable number of HCON sessions, but the system load may not be appreciably reduced. In this case, adding real (physical) memory to your local system can enhance system performance. To determine the amount of real memory installed on your system, enter:
lsattr -E -l sys0
Increasing the number of allowable user processes, available system paging space, or the default limits in the SNA Services /dev/sna server can also enhance system performance. See "Tuning Local Systems When Using SNA Services with HCON" for detailed information about these tasks.
