6100 ADCCP Programming Manual

Application Tasks
Writing Applications that Use ADCCP
4–24 069225 Tandem Computers Incorporated
In general, the responses indicate the following kinds of problems:
Hardware or resource allocation errors in a 6100/3650 CSS or 3605/6105
communications controller
Invalid request or request format
Cancellation of a pending request by another (for example, a MODE SET cancels
all pending data transfers for the station)
Station malfunctions
Modem errors.
Invalid frames received on the line
Unexpected mode-setting frames received
Sometimes recovery entails repeating the last request or making a small correction and
then repeating the request. Recovery may also involve:
Issuing new mode-setting sequences
Disconnecting a station or the line
Stopping the line until the problem has been solved
If multiple applications use the same line, you should distribute error-recovery
strategies among them to avoid contradictory or redundant requests. (Even
redundant requests can cause problems because by the time the second request
arrives, it may cause an undesirable state transition). The software running in remote
stations is also important to consider when trying to avoid contention in recovery
between stations on a link.
Error Handling and SYSGEN
Several SYSGEN parameters have an impact on error recovery. They are:
AUTOCLOSE Determines whether opens are closed. If so, applications must close
the line and open it again to use it. For example, AUTOCLOSE is
used if the line must be downloaded because of a hardware
problem.
AUTOCONF Determines whether the configuration block is sent from the host
after a download, replacing the current configuration; if the
application made configuration changes, it must restore them
before continuing.
AUTOLOAD Selects whether the line is downloaded or declared down under
certain error conditions.
NOAUTOSTOP Determines whether CP6100 makes a STOP request after closing the
opens; if so, a switched connection is lost.
For more information about these parameters, see the CP6100 I/O Programming
Manual and the System Generation Manual for CP6100. To find out how the application