In an SNA environment you can determine which server initiates the connection request and which server waits for an incoming connection request.
To have your server initiate the connection, you can configure the controller description to dial the destination. If no connection is established, your controller description automatically switches to answer mode.
To have your server wait for incoming calls, you can configure the controller description to answer the incoming calls. You specify the mode through the Initial connection (INLCNN) field of the controller description:
SNA controller descriptions use dial mode to send a connection request to a remote device. Dial mode typically starts when varying on the controller description. However, if the DIALINIT parameter is set to *DELAY, dial mode will not begin until an application opens a file that uses the connection. During the dialing process, the server polls the remote device to determine if the device is available. If the remote device is available, the connection process continues. Successful connection is still possible even if the local and remote devices dial each other simultaneously.
The controller description fields below set the frequency and duration of the poll:
If the remote device answers the poll within the time specified by the parameters, your server proceeds with establishing the connection. If not, your server sends an inquiry message (CPA58E0 or CPA57EF) to the configured message queue. This message indicates that a connection attempt failed and that the controller description is now in answer mode.
If you specify answer mode, the input/output adapter (IOA) does not originate connection requests, but will respond to incoming connection requests. Servers with controller descriptions that are configured with dial mode will initiate and accept connection requests. However, APPC controllers that are user owned (CTLOWN = *USER) must be varied on before the server can respond to connection requests.