OSI/AS Programming Manual

Overview of OSI/AS Session Layer Support
Introduction
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The duplex functional unit allows you to operate in duplex mode over a
connection. In this mode, data can be transferred in both directions
simultaneously. A particular connection uses either the half-duplex or the duplex
functional unit, but not both.
The typed data functional unit allows you to send typed data over a connection,
ignoring any token restrictions.
The capability data exchange functional unit allows you to send and receive a
limited amount of user data while no activity is in progress. This functional unit
can be selected only if the activity management functional unit is also selected.
The major synchronize functional unit allows you to structure the exchange of
data between your application and the remote application into a series of dialog
units.
The minor synchronize functional unit allows you to structure the exchange of
data within a dialog unit.
The resynchronize functional unit allows you to reset the connection to a defined
state after a problem.
The exceptions functional unit allows you and the service provider to issue
exception reports. This functional unit can be selected only if the half-duplex
functional unit is also selected.
The activity management functional unit allows you and the remote application to
define logical pieces of work as activities and to organize the flow of
communication accordingly.
The expedited data functional unit, described in the session service standard, is not
supported.
How Is the Session Version
Selected?
OSI/AS supports both version 1 and version 2 of the Session Layer. Session version 2
provides additional capabilities not available in version 1. One example is the ability
to send and receive limited user data (user data sent with primitives other than data
and typed data primitives) in larger amounts and with most primitives that do not
contain user data in session version 1.
The session version is set during configuration, using the SCF interactive interface or
the DSM programmatic interface. For details about configuring the OSI/AS
subsystem using SCF, refer to the SCF Reference Manual for Tandem OSI/AS or the
Tandem OSI/AS Management Programming Manual.