TRANSFER Programming Manual

Limiitations of the TRANSFER Delivery System
An Overview of the TRANSFER Delivery System
40970 Tandem Computers Incorporated 1–5
Advantages of the
TRANSFER Delivery
System
The TRANSFER delivery system relieves application programs of several tasks that
they would otherwise have to perform. For example, the TRANSFER delivery system
can:
Deliver packages composed of multiple components
Stage transactions over time
Monitor the computer network for availability of remote resources
Manage the routing of packages to multiple recipients throughout a network
Ensure reliable package delivery, even in the event of failures, while preventing
duplicate deliveries
Provide temporary storage for items and packages
An application can specify the earliest and latest times that a package can be delivered.
If the package cannot be delivered within that time window, the TRANSFER delivery
system returns it to the sender. An application also can specify priorities for packages
so that if many packages are sent within a short time, those with the highest priorities
are processed first.
Recipients of packages need not be available to receive them. If a network node is
unavailable when the TRANSFER delivery system attempts to deliver a package,
delivery takes place as soon as the node does become available. If the recipients are
unavailable, the TRANSFER delivery system stores packages for those recipients, who
can collect them at their own convenience.
When an application requests the TRANSFER delivery system to deliver a package,
that package will reach its destination exactly once. If a hardware failure occurs, the
TRANSFER delivery system ensures that a package is neither lost nor delivered twice
to any recipient. An application also can define certification criteria by specifying, for
example, that a sender is always notified in some way when all recipients have
received packages that were sent.
Limitations of the
TRANSFER Delivery
System
Consider the following before you decide to use the TRANSFER delivery system:
The TRANSFER delivery system emphasizes reliability of delivery rather than
speed of transmittal. The TRANSFER delivery system cannot guarantee that a
package will be delivered at a specific time and cannot predict how much time a
package will spend in transit. Thus, the TRANSFER delivery system is unsuitable
for applications such as real-time communication.
The TRANSFER delivery system does not attempt to deliver packages in the same
order that they are sent. Your application program, however, can arrange to
process packages upon receipt in the order in which they were transmitted.
Although the TRANSFER delivery system allows a package to contain any kind of
data, the TRANSFER delivery system does not interpret or process the data in the
packages. That is the responsibility of your application program.