METHOD AND APPARATUS FOR PERIPHERAL DATA HANDLING HIERARCHIES

Data supplied to a data storage system by a host processor has one of two use status. A first use status is that the supplied data is to be retentively stored in the data storage system. A second use status is that the supplied data is exempted from the retentive storage requirement. An example of exempted use status is that data only temporarily stored in the data storage system, i.e. is transitory. A second example is data that is being manipulated prior to retentive storage, data that is temporarily volatile. Termination of the exempted use status results in either discard or a retentive storage of the exempted use data. Data integrity controls for the exempted use status data are described. The invention is described for a data storage hierarchy environment having a volatile cache and a magnetic recorder as a backing store. The exempted use data need be stored only in or primarily in the cache while retentive data is primarily stored in the retentive store and selectively in the cache.