Abstract: A data processing system is disclosed which includes a control system with a buffer store connected to a central processing unit to receive data items before they are transferred to a secondary journal store. A monitoring system keeps a check on the rate at which data items are placed in the buffer store by setting a sample value, which is a count of the accumulated size of items in the buffer store, and a sample time which is a period, such as one second, considered a reasonable waiting time for a transaction, either of which when reached can cause the contents of the buffer to be transferred to the secondary journal store. If the sample time is reached before the sample value, then the value is increased.