About Directory exits

What is a directory exit?

You can use the directory exit task to modify the parameters used to establish an exit connection with a remote partner in server or requester mode. A user subprogram can be called each time a session with a partner, or a set of partners, is opened depending on the Transfer CFT parameter setting.

Use a directory exit to:

  • Server mode - to replace the standard checks performed by Transfer CFT when a remote partner requests a connection
  • Requester mode - to provide, supplement or modify the parameters Transfer CFT requires to establish network and protocol connections with a remote partner

The directory exit parameters can include:

  • Network name
  • Password
  • Remote partner address
  • Remote SAP - service access point
  • Final protocol to be used

The directory EXIT can only be called once during the protocol connection phase, or start of protocol session.

Server mode

When a connection is indicated, Transfer CFT knows the network name and the calling partner’s password as well as the protocol to use for the communication. If the corresponding CFTPROT object contains the identifier of a directory EXIT task, the monitor gives control to this task that performs user checking, calling partner’s network name and password, call time slots, and so on.

You can:

  • Request Transfer CFT to perform your own standard checks
  • Accept the call
  • Refuse the call

In this mode, regardless of the protocol used, the EXIT task takes control at each protocol connection, even in the case of a transfer sequence over a single physical connection. In the case of a transfer sequence over a protocol connection, the EXIT task does not take control.

The EXIT can perform checks on a partner:

  • Known to Transfer CFT and defined in a CFTPART object
  • Unknown to Transfer CFT when there is no CFTPART object

It can accept or refuse network and protocol connections.

Even if all partners are unknown to Transfer CFT, the monitor needs the partner file to operate.

Requester mode

In requester mode, you can:

  • Request Transfer CFT to perform your standard checks before establishing connections
  • Accept to establish connections
  • Refuse to establish connections

The partner may be known, defined in a CFTPART object, or unknown to Transfer CFT.

Even if all partners are unknown to Transfer CFT, the Transfer CFT needs the partner file to operate.

At the time of a connection request, Transfer CFT knows the CFTPART object associated with the PART parameter of the SEND or RECV command. The Transfer CFT uses the first protocol of the CFTPART object as communication protocol, the other protocols defined in this object being used as backup protocols.

The first protocol choice criterion is:

  • The partner is known to Transfer CFT: there is a CFTPART object corresponding to the partner. The first protocol of the CFTPART object containing an EXIT directory identifier is chosen. If no protocols of this command contain an EXIT directory identifier, the first protocol is chosen
  • The partner is unknown to Transfer CFT: there is no CFTPART object corresponding to the partner. The first protocol of the CFTPARM object that contains an EXIT directory identifier is chosen. If none of the protocols of this command contains an EXIT directory identifier, the transfer is abandoned, and the request changes to the "K" state

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