Exchange/RJE Manual

CONTROL Procedure
Exchange/RJE System Procedure Calls
5–14 104698 Tandem Computers Incorporated
End of Transmission
The end-of-transmission operation ( operation = 13) has two functions. Normally, it
tells the remote system that your program has finished transmitting. The operation
also gives up control of the line, returning both systems to the control state. In the
control state, either system can bid for the line (that is, bid for the right to transmit to
the other system).
End-of-transmission can also be used to abort an operation if an error prevents your
program from continuing. If your program is receiving a transmission, it can send an
EOT to the remote system, telling it to abort the transmission. This use is dependent
on the programming of the remote system; not all systems abort a transmission on
receipt of an EOT.
If your program is sending a transmission when it discovers an error, it can send an
EOT without prefacing it with an ETX. This indicates a problem and causes the
remote system to abort the receive operation.
Disconnect
The disconnect operation is used with switched lines. It tells the remote system that
your program has finished transmitting and that the remote system should disconnect
from the telephone line. The operation places both systems in the disconnected state.
A new connection must be established before either system can bid for the line. If you
omit this operation when using a switched line, both the local system and the remote
system will disconnect from the line after the disconnect timeout has elapsed (usually
20 seconds).
While not normally used on nonswitched lines, the disconnect operation is allowed on
nonswitched lines, where it functions as described here except that no physical
disconnection of the data communications line takes place.
You can use the disconnect operation in place of an end-of-transmission operation if
your program is not expecting to receive output from the remote system and you want
to stop.
Ending a Send Operation
After a send operation, your program should always perform an end-of-text operation
before performing an end-of-transmission or disconnect operation. If any records are
in the line server’s buffers waiting to be transmitted, those records will be lost if an
end-of-text operation is not performed before an end-of-transmission or disconnect
operation. The only way to guarantee that the line server’s transmission buffer is
empty (and all records have been transmitted) is to perform an end-of-text operation.