In OSI TP communications, the attributes of an association are determined by the system that requested establishment of the association. Calling refers to issuing an association establishment request, and called refers to receiving such a request. The system that issues an association establishment request is the calling system, and the system that receives such a request is the called system.

To request a service from OpenTP1 for a remote system, an association established by a calling OpenTP1 system is used. Associations established by a called OpenTP1 system are used principally for error recovery communications.

If you specify in the TP1/NET/OSI-TP-Extended definitions a request for establishment of an association during system startup, an association is established when the system starts. Whether the local system is to be the calling system or the called system depends on the specification of the nettalccn protocol-specific definition in the TP1/NET/OSI-TP-Extended definitions.

Make sure that you specify a request to establish association during system startup in the TP1/NET/OSI-TP-Extended definitions.

When the OpenTP1 system terminates normally, the association is released successfully. If the OpenTP1 system or the remote system terminates abnormally, abnormal release of the association results.

The following OpenTP1 definitions are required in order to perform client/server communications using OSI TP:

• XATMI communication service definition
• Network library definitions (TP1/NET/Library and TP1/NET/OSI-TP-Extended definitions)

OSI TP communications are enabled when correspondence between the XATMI communication service and TP1/NET/OSI-TP-Extended is established by the above definitions.