In traditional StartHostNotification there are options provided for differentiating between screen area and the OIA (operator information area) changes. FlyHLLAPI ignores these settings and will flag a change any time there is a new buffer which modifies any character in the screen session.
Use Start Host Notification as part of a screen synchronisation scheme which monitors each screen change in an event-driven efficient manner. The standard screen transition should be implemented with:
Start Host Notification (23)
Send Key (3) (with AID key in TN3270/TN5250 and a action-causing key in VT)
Wait
LOOP
IF--The next screen is ready OR
There is an error condition
BREAK
ELSE
Pause (18)
END LOOP
The above pseudocode represents an efficient example for monitoring change to a screen following the sending of keys that will change the active screen. This utilizes an internal semaphore rather than a polling mechanism for tracking any changes to the screen. This use of HLLAPI calls has also been implemented so that no race condition between the high-level logic and screen updates can occur where an update will be missed.
Data String: First character: blank or a letter ID of the session to monitor. With FlyHLLAPI it is generally recommended that this be blank and that the thread owning the session be the one making the Start Host Notification call.
Returns
RetCode: WHLLOK
