Managing HCON

The Host Connection Program (HCON) is a software package for communication between a local system and one or more System/370 mainframe hosts. To communicate with a mainframe host, HCON establishes a session, a period of interaction with the host system.

HCON system management includes working with:

• Sessions
• Display emulation
• Printer emulation
• Processes
• File transfer process
• Connections and adapters

HCON establishes multiple sessions with System/370 mainframes. Each session emulates either a 3278/79 display or a 3286/87 printer. A session emulating a display is a display session. A session emulating a printer is a printer session. HCON provides file transfer capabilities within display sessions. It also includes the High-Level Language Application Programming Interface (HLLAPI) to write programs that communicate with mainframe host programs.

Each HCON user can have up to 26 sessions, allowing one or more simultaneous invocations of session to communicate with one or more hosts using different session characteristics and communication protocols. The parameters defining the session characteristics are established by a session profile.

To communicate with a mainframe host, HCON uses one or more of the following:

• 3270 Connection Adapter in Distributed Function Terminal (DFT) mode
• Host Interface Adapter (HIA)
• Group of adapters supported by System Network Architecture (SNA) Services/6000
• Group of adapters supported by Transmission Control Protocol/Internet Protocol (TCP/IP)

If the local system has more than one of these devices installed, users can implement different devices for different HCON sessions:

The system can have any combination of supported adapters:

• Each 3270 Connection Adapter supports up to five sessions.
• HIA supports up to 16 sessions.
• Each SNA Node T2.1 attachment supports up to 253 logical units (LUs) per connection.
• For TCP/IP, the maximum number of sessions per connection depends upon the user's system resources.

Note: The total number of HCON sessions you can start depends on the availability of various system-wide resources such as message queues. Consult the documentation specific to the AIX version for the upper limits on such system-wide resources.

The following table lists the number of message queues required to start an HCON session for each type of session.

SNA DFT display	10
Non-SNA DFT display	8
Non-SNA DFT printer	8
SNA standalone printer	8
SNA standalone display	8
TCP/IP display	8

The AIX operating system constrains the number of HCON sessions you can start based on the maximum number of message queues and the number of message queues already in use.

HCON Users

Before using HCON, the user must be defined as an HCON user. An HCON user can create session profiles, then:

• Establish display or printer sessions with a mainframe host.
• Use the file transfer facility (the fxfer command).
• Run programs written with HCON HLLAPI.

To define a new user to HCON, you must have root authority. Add or remove an HCON user with the smit hcon or the mkhconu command by specifying a valid user logon name. When you remove a user, the name you specify must be that of a registered HCON user.

HCON uses an Object Data Manager (ODM) database to store information about users. When an HCON user is registered, an entry for that user is created in the ODM database, using the system defaults for session information. Thereafter, each time the user creates a new session, HCON changes the user's defaults in the ODM database to match the values set for the last session the user created.