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3270 Host Connection Program 2.1 and 1.3.3 for AIX: Guide and Reference

HCON File Transfer Process

The HCON file transfer program transfers files between a local system and a mainframe host. With the corresponding version of the 3270 File Transfer Program (IND$FILE or its equivalent) installed, the host operating system for transfers can be:

For the VSE/ESA operating systems, the file transfer program is provided as part of the VSE base. The additional host transfer program is not needed. If you want to perform a file transfer to CICS/VSE, the transfer program should be VSE/ESA.

When a file is transferring from a local system to a host, the file transfer is uploading. A transfer from the host to the local system is downloading. The HCON file transfer features support text and binary data. The file transfer program consists of two modules:

fxfer process Interprets the file transfer requests, forms file transfer request queues, and sends the requests to the appropriate dfxfer process. The fxfer process is started from the command line by the fxfer command. The status of the file transfer operation is reported to a terminal, a file (if invoked with the fxfer command), or to a program (if invoked by a program).
dfxfer process Transfers files. The dfxfer process is started either by:
  • fxfer process
  • fxfer command
  • API program issuing the g32_fxfer function
  • HCON utility program

Each dfxfer process is associated with one display session. Multiple file transfer requests using the same session are queued using the same dfxfer process. The dfxfer process remains logged on to the host indefinitely, based on the file transfer wait period specified in the session profile.

File transfers are either:

asynchronous When the user starts additional file transfers without waiting for the first one to complete. Each request goes in a queue used by the dfxfer process associated with the display session. Up to 580 file transfers can be queued at one time.
synchronous When the file transfer is processed immediately. If a current file transfer has not completed, additional synchronous file transfer requests generate a host connection busy message.

File transfers are either:

explicit When the user must establish a session with the host and log on before starting the file transfer.
implicit When the fxfer process checks for the appropriate session. If the session exists, the fxfer process connects to it and starts the dfxfer process for the file transfer. If the session does not exist on the local system, the fxfer process starts the dfxfer process. The dxfer process:
  • Invokes the session by starting an e789x process.
  • Logs on to the host.
  • Transfers the file.
  • Logs off the host.
  • Ends the session.

If a file transfer wait period is specified, the dfxfer process logs off the host and terminates the session only after the specified period of inactivity has elapsed.

Note: If the requested session exists, it could have been started explicitly with the e789 command or implicitly by a previous file transfer.

A file transfer can be interrupted before it is completed. A file transfer can also be interrupted by any unrecoverable communication error. When interrupted, the state of the transfer is saved. The transfer can be restarted without loss of data. See "Recovering from Interrupted HCON File Transfers".

You can create a shell procedure to specify parameters for similar file transfers that are performed frequently. See "Creating HCON File Transfer Shell Procedures".

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