Cancels the currently active database server request. This function checks to make sure a database server request is active
before sending the cancel request. If the function returns 1, then the cancel request was sent; if it returns 0, then no request
A non-zero return value does not mean that the request was canceled. There are a few critical timing cases where the cancel
request and the response from the database or server cross. In these cases, the cancel simply has no effect, even though the
function still returns TRUE.
The db_cancel_request function can be called asynchronously. This function and db_is_working are the only functions in the
database interface library that can be called asynchronously using a SQLCA that might be in use by another request.
If you cancel a request that is carrying out a cursor operation, the position of the cursor is indeterminate. You must locate
the cursor by its absolute position or close it, following the cancel.