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If your system is particularly difficult to access physically, another strategy is to
protect it with an Uninterruptible Power Source (UPS) and a phone-line surge
protector.
In case recovery becomes necessary, shut down your system using established
procedures. Disconnect the power cable and press the power button to drain
capacitance while power is disconnected. Disconnect and reconnect modem power,
and then reconnect system power to completely reinitialize your system.
Transfer of a Modem Session
Because many modem command variations exist, the sample modem configuration
files located at the end of this appendix have been written to capture the largest
number of workable modem settings.
The modem command &Dn (where
n
is a number) generally sets the modem
response to the Data Terminal Ready (DTR) signal from the server's serial port. The
desired response is that the modem will hold a connection while DTR is enabled,
and drop the connection when DTR is released. Using this mechanism, the server
hangs up on a connection under normal conditions.
Consult your modem manual for its specific response scheme for the &Dn command.
Two strategies are available for dealing with the modem's response to DTR:
Recovery
Prevention
Before you use one of these strategies, determine if your server's modem is set up
correctly to respond to DTR.
With the remote terminal connected to serial port 1 and defined as the Primary
Console Device, there are two tests you can perform:
1. Will the modem drop the connection after the System initialization complete
message displays at the remote terminal?
If Yes, the modem is set up correctly.
If No, try another &Dn setting for your server's modem. See your modem
manual for this information. The &Dn command appears in three places each in
three of the sample modem configuration files, as follows:
2. Will the server's modem disconnect when the power drops? You can make this
observation at the remote terminal by commanding your server to shut down and
Appendix D. Modem Configurations 183