Journal back-up storage control for a data processing system

Claim 1

In a data processing system involving information retrieved in a data base comprising a central processing unit, a main store, a secondary non-volatile store and a plurality of input/output terminals connected to the central processing unit, in which a plurality of transactions may take place concurrently and any data item which will be changed by a transaction is recorded on the secondary non-volatile store before the change is committed, the system also including a buffer store connected to the central processing unit and arranged to receive data items from the main store when a transaction is about to change an item, the improvement comprising control means to set a read out value for the number of items receivable by the buffer store to induce a read out and to provide a time interval, means to initiate a transfer data base changed data items hel in the buffer store in said secondary store whenever the read out value is reached or the time interval expires, means to increase the read out value when the number of data items readout of the buffer store exceeds the existing readout value, and means to decrease the readout value when the number of data items readout of the buffer store is less than the existing readout value.