Device History Events

 

Q. When a user clicks the UI to look at key history, what can we say about how long this history has been running?

 

A. It’s not based on time.  The terminal agent has a fixed-size memory buffer for each device.  For keystrokes, it’s more like 'the buffer will typically hold nn keystrokes.'    The current size is approximately 750 bytes / 50 keystrokes.

Additional notes:

To save memory and bandwidth, not every originating event will result in a history queue event. This is most pronounced with display devices. If a display command by an application results in no change to the display, that event is not recorded in the history queue.

The controller agent also has a per-device memory buffer and this buffer may be a different size than the terminal buffer.  The controller agent puts keystrokes into its buffer when a terminal is being monitored.  If a 2nd client comes up and wants to monitor a terminal, the 2nd client will be given history from the controller agent instead of the terminal agent (in order to minimize POS loop/lan traffic).  The controller agent's buffer is flushed when there are no more clients.

Some other current defaults for device history buff sizes:

40 2x20 display lines
10 cashdrawer open commands
30 receipt lines (38 chars each)
50 vdisplay display lines (80 chars/attrs each)

Future version considerations:

We are likely to end up with a couple of versions of the terminal agent:  small and normal.  The small version may have smaller history buffers than the normal version.

We may make the terminal device history buffer sizes configurable if it seems like default sizes can’t meet the needs of different customers.

We will likely have an optional feature that allows keystrokes and other device history to be saved on the controller.  For example, 'save past n days worth of device history for all terminals for these devices.’