Some operations can take a long time to complete. For example, a complete re-schedule of your whole order book could take as much as an hour if you have thousands of orders active. The system employs a device called a monitor whenever it performs an operation that is likely to take more than a few seconds. The monitor gives you feedback on the progress of the operation so you can see it is working and not just ‘stuck’, and also allows you to pause or cancel the operation. A typical monitor is shown below:

Pressing the Click here to pause or cancel button will pause the operation and present an option to cancel it. Like this:

If the operation involves committing a transaction to the database it will automatically resume after a few seconds unless it's cancelled. If a transaction commit is cancelled, the whole transaction is rolled-back to the beginning.