Session Management

This chapter describes INBOUND and OUTBOUND session management.

1. Sessions

A Host-link system contains multiple processes which manage and maintain sessions. The number of processes present in the Host-link system can be adjusted using the MIN and MAX parameters in the SERVER section of the Tmax configuration file. The processes can handle services up to the maximum number of sessions provided by a single link session. If the number of sessions is insufficient, services are automatically transferred to another available Host-link process.

The sessions managed by the Host-link system are classified as INBOUND and OUTBOUND sessions, based on the host.

2. INBOUND

INBOUND sessions are used by an open environment system to send requests to the host system. The sessions are shared among processes.

There are two types of modes for an INBOUND session: pool mode and dedicate mode. The type of mode used depends on how the session is used.

Pool Mode

Services are requested using currently available sessions. When a service is requested to a Host-link process through the Tmax system’s load balancing feature, the Host-link process requests the service from the host using an available session it holds. If no available session exists, the service request is transferred to another Host-link process.

In pool mode, sessions are assigned to each task, and tasks use their assigned sessions to request services. To use this mode, specify a user header in the Host-link configuration file and define the session type of the header. Services can be requested using the desired session.
Dedicate Mode

Services are requested using sessions specified by particular values. This mode is used to maintain sessions for each terminal. Unique numbers are assigned to each terminal, and the terminals use the sessions corresponding to the assigned numbers to request services from the host system. The existing host system maintains the sessions of each terminal and manages the timing of cash flows that occur in the terminals.

SNA LU 0

SNA LU 0 supports both pool mode and dedicate mode.

SNA LU 6.2

SNA LU 6.2 supports only the pool mode. The following two methods can be used to communicate between systems.

Method	Description
DPL Method	DPL is used in Tmax’s interactive communication mode and deliver services through a mirror provided by the host. DPL is only supported in INBOUND services.
DTP Method	DTP is used in Tmax’s synchronous and asynchronous communication modes, and connects directly to host services. This method is supported by both INBOUND and OUTBOUND services. Depending on the setting specified in the Host-link environment configuration file, this method can also be supported in either the INBOUND or OUTBOUND service.

Method

Description

DPL Method

DPL is used in Tmax’s interactive communication mode and deliver services through a mirror provided by the host. DPL is only supported in INBOUND services.

DTP Method

DTP is used in Tmax’s synchronous and asynchronous communication modes, and connects directly to host services. This method is supported by both INBOUND and OUTBOUND services. Depending on the setting specified in the Host-link environment configuration file, this method can also be supported in either the INBOUND or OUTBOUND service.

For more information about communication modes, refer to Tmax Administration Guide.

3. OUTBOUND

OUTBOUND sessions are used by the host system to send a request to an open environment system. As OUTBOUND sessions are used by the host system, Host-link, a CUSTOM_GATEWAY in the open environment system, cannot share the sessions among processes.

SNA LU 0

OUTBOUND sessions of SNA LU 0 consist of general sessions, BID sessions, and ROP sessions.

Session	Description
General Session	Used for requesting services provided by Tmax. When a service is requested using this session, the Host-link process requests the service from the Tmax system in the method defined in the Host-link configuration file.
BID Session	Used for delivering urgent messages to a specific region or person. When a service is requested using this session, the Host-link process requests the service from the Tmax system in the method defined in the configuration file.
ROP Session	Used for delivering large amounts of data that cannot be sent through a BID session. Documents that were previously delivered by mail can be sent to a specific terminal in the target region using this session. This session also requests services from the Tmax system using the method defined in the configuration file.

Session

Description

General Session

Used for requesting services provided by Tmax. When a service is requested using this session, the Host-link process requests the service from the Tmax system in the method defined in the Host-link configuration file.

BID Session

Used for delivering urgent messages to a specific region or person. When a service is requested using this session, the Host-link process requests the service from the Tmax system in the method defined in the configuration file.

ROP Session

Used for delivering large amounts of data that cannot be sent through a BID session. Documents that were previously delivered by mail can be sent to a specific terminal in the target region using this session. This session also requests services from the Tmax system using the method defined in the configuration file.

SNA LU 6.2

OUTBOUND sessions of SNA LU 6.2 are used to request services provided by the Tmax system. When a service is requested using this session, the Host-link process will request the service from the Tmax system in the method defined in the environment configuration file.

4. Session Troubleshooting

Session issues are resolved using the troubleshooting methods provided by the Tmax system. Troubleshooting for Host-link is classified into the following three types.

4.1. Sessions

If a Host-link process detects that a specific session is inactive, it terminates the session with the SNA server first and then attempts to reconnect to the host according to the procedure used to establish the first session. As a timeout is applied when attempting to connect, multiple connection attempts do not cause system load.

Session troubleshooting is performed in the following order.

Terminate the session with the SNA server.
Initialize the session on the SNA server.
Send the session information to the host.
If a bind session is received from the host, then the session has been successfully established. Otherwise, repeat the procedure from Step 3.
Register the session.

4.2. Link Sessions

A single Host-link process only manages only one link session and regularly monitors it. If a link session changes from inactive to active, all its sessions will attempt to connect to the host. A single link session can support up to 256 sessions. If a link session becomes inactive, all the connected sessions are disconnected from the host.

Link session troubleshooting is performed in the following order.

Temporarily disconnect the session from the Tmax system.
Disconnect the session from the SNA server.
Monitor the link session.
If a link session is successfully established, only one of its sessions attempts to connect.
When a session receives a bind session from the host system, all link sessions are connected to the host.
Reconnect to the Tmax system and perform scheduling tasks.

4.3. Session Pool

A single Host-link process can manage up to 256 sessions, and multiple Host-link processes are used as a single pool. If a Host-link process fails to find a session to execute the requested service, the data is forwarded to another Host-link process that has available sessions.

Because a single Host-link process in the Host-Link system can manage only up to 256 sessions, the Host-link system cannot handle more than 256 service requests simultaneously. In such cases, the data is forwarded to an available session within the Host-link system, allowing the services to be processed.

A Host-link system is a single server registered in the SERVER section of the Tmax configuration file. Multiple Host-link processes can be configured in a single Host-link system, and the number of processes are specified with the MIN and MAX parameters in the SERVER section. For more information about the SERVER configuration, refer to SERVER Section.