Re: Interupting an rpg sql search

Hi Tim,

I would like to be able to stop the search by hitting a key (say esc
key tied to an attention program).

The only way that I know of is to run the SQL search in a separate job (a background job) where you can get the user's input (via an INVITEd screen, etc) and end the background job if the user presses the abort key.

(Personally, I'd use something like F12=Cancel or a different F-key rather than trying to use ESC, which isn't a key on the 5250 keyboard. ATTN would work, but people like to be able to map that to a program or utility that they want to open in the middle of another application. So I'd just use an F-key of some sort.

I'd use data queues to communicate with the background job, since both the display file is also able to add records to a data queue when the user presses a key. That way, your code has only one object to wait on, the data queue. Depending on the type of record, you'll know whether input came from the display or the SQL search.

If the user wants to cancel, you just issue an ENDJOB statement against the background job. If for some reason, the job is in a state where it can't be cancelled (such as the middle of building a temporary index) the job will keep running until it's able to end, and then finally end. Your program need not wait for it to do that, so your user can happily go about his/her business.

The only other possibility I can think of is signals. I've never tried using a signal to abort an SQL statement, and I don't know if it's possible... but I've used it to abort other things (sockets, displays, interative CL commands, etc.) and it has worked. If signals work with an SQL statement, they might let you do this all in one job. The problem is, if this isn't documented anywhere by IBM, who knows if it'll work today and not tomorrow? Or if it won't even work today... or if it'll mess something up... hard to say. But it's interesting to consider as an intellectual exercise.