Chapter 3. Operating NetView FTP V2.2.1 MVS - IBM

Automatic Restart of an OSI File Transfer
All information concerning a request is written to a recovery file. This file contains
information about requests that have been passed to OSI/File Services and for
which NetView FTP V2.2.1 MVS has not yet been notified as being completed.
Each OSI server has its own recovery file.
A recovery file keeps information necessary for the OSI server to continue processing
the currently active requests following an abnormal termination. If the OSI
server terminates abnormally, the current request is set to waiting. If the queue
handler terminates, all outstanding requests are set to waiting. When the OSI
server is restarted, it knows from its recovery file which file transfer requests are
new and which have already been passed to OSI/File Services.
The OSI server uses the recovery file to rebuild its Local Request Table. This table
is updated after each significant change of the server status. When the contents of
the recovery file are put into the Local Request Table at initialization time, the
recovered entries are marked. It does not matter whether the control structures
corresponding to each request are destroyed, because each request must be
obtained from the queue handler again before the request can be completed.
If one of the recovered requests was canceled by the operator or the filestore
owner, the result is still available for the OSI server as the issuer of the request.
This ensures that all recovered requests are finished in the server and removed
from the Local Request Table.
Manual Restart of an SNA File Transfer
You can manually restart a transfer, to recover from errors that automatic transfer
restart cannot handle, or when automatic transfer restart is not desired.
How the Manual Restart Facility Works
The following items characterize NetView FTP V2.2.1 MVS’s manual transfer restart
facility:
� If NetView FTP V2.2.1 MVS is not able to restart a transfer automatically, or if
you specify that you do not want it to try to automatically restart a transfer, the
server that obtains the file-transfer request marks it with the status finished
and writes it back to the request queue. Both servers tell the appropriate users
about the interruption in the file transfer.
The file-transfer request is not rescheduled until you restart it. You can restart
only those file-transfer requests that are marked restartable.
When the request is scheduled, a checkpoint record from the checkpoint data
set is used to restart the file transfer. It is restarted from either the recorded
checkpoint or the beginning of the file depending on the value you specified for
the Restart Point parameter. The sending and the receiving servers position
their data sets to match with the checkpoint and the file transfer is resumed.
A special message is issued by the server that indicates if the file transfer is
started from the recorded checkpoint or the beginning of the file.
Appendix B. Transfer Error Recovery 191