Exchange/RJE Manual

Operational Considerations
Using the Exchange/RJE Command Interpreter
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Operational
Considerations
There are a number of operational considerations you need to be aware of when using
the Exchange/RJE command interpreter. These considerations are discussed below.
Single User Only Exchange/RJE does not support multiple concurrent users over a single data
communications line. At any given time, only one Exchange/RJE line server can be
connected to a given data communications line and only one user can be connected to
that particular line server. You can, of course, have multiple users using separate line
servers and separate data communications lines at the same time.
If you attempt to connect to a line server or a data communications line that is already
in use, the connection will be denied and an error message will be displayed. To
recover from this error, you must wait until the other user executes a DISCONNECT
or EXIT command, which releases the data communications line and the line server,
and then attempt the connection again.
The User-Exit Procedure This section contains some considerations for using a user-exit procedure.
The user exit is invoked only if the DIAL parameter is supplied in the CONNECT
command. To communicate over leased lines from a line server with a user-exit
procedure installed, simply omit the DIAL parameter in the CONNECT command.
Every user who needs to specify or change the user library for a line server must have
write-access to RJESV, the line server object file. This means that every user who uses
the command interpreter to start a new line server needs write access to RJESV.
Every line server running simultaneously from the same RJESV file must use the same
user library. If a line server is already running from a given copy of RJESV, you
cannot specify a different user library when you start a new line server (you will
receive an error message if you attempt to do this).
If your installation requires the simultaneous use of two or more user-exit procedures,
you must use multiple copies of the RJESV file—one for each different user library.
These different copies of RJESV must reside in different subvolumes. Use the
PROGRAM parameter in the SET command to direct the command interpreter to the
appropriate copy of RJESV. If you do not specify this parameter, the default is for the
next CONNECT command to start the line server from the RJESV file that resides on
the same system, volume, and subvolume as the command interpreter. See the SET
command description in Section 3 for more information.
If you want to use the automatic calling unit (ACU) support built into Exchange/RJE
for automatic dialing, you must use the supplied, default user exit in RJELIB.
For information on writing a user-exit procedure, see Appendix E.
Nowait Operation The command interpreter performs send and receive operations as nowait I/O. When
you execute a SEND or RECEIVE command, you will see the command interpreter’s
prompt before the send or receive operation is completed.
While a send or receive operation is in progress, you cannot start another send or
receive operation or initiate another connection. Only one connection and one send or
receive operation is allowed at a time.