Exchange/SNA Manual

Programming Considerations
Using the Exchange/SNA Programmatic Interface
104700 Tandem Computers Incorporated 4–7
Nonrecoverable Errors
You generally cannot program your applications to recover from data communications
errors or problems communicating with the host, especially if a transmission is in
process at the time of the failure. If you receive a serious error, such as error 140
(modem problem) or 183 (session ended), you need to intervene to:
Stop the line server, if it is not already shutting down or terminated.
Restart the line server and re-establish the connection to the host.
Restart the transmission that was in process at the time of the error. If you were
receiving data from the host, and the host has already purged your job, you need
to run the job again before receiving the data. Set the PURGE parameter off if you
want the host to retain your job output until you successfully receive it.
Error Numbers
In the event of an error or a warning, the call to FILEINFO returns the error number.
For a complete list of all Tandem defined error numbers and their meanings, see the
Guardian Procedure Errors and Messages Manual.
Table 4-2 lists the most common errors that pertain to the Exchange/SNA line server
or the underlying communication subsystem.
Table 4-2. Exchange/SNA Line Server Errors (Page 1 of 2)
No. Meaning
0 No error occurred; the operation completed successfully.
1 An end-of-file was read, or an end destination selection (EDS in a type 1 function
management header) was received from the host system.
2 You have attempted an operation that is not allowed on the type of file you specified.
11 The specified file is not in the directory.
12 The file (subdevice) you specified is in use. Wait and try the operation later, or use another
subdevice.
13 The specified file name does not conform to the rules for file names. For example, the
subdevice specification omits the required pound sign ($sna.rd1, which is incorrect, instead of
$sna.#rd1, which is correct).
14 The specified device does not exist. Typically, this means you have specified a nonexistent
subdevice.
16 The file you specified has not been opened yet. The file must be open before you can perform
I/O operations on it.
21 You specified a value that is out of range. Typically, this means that the number of bytes to
transfer in an I/O operation is too large or too small.