transactions are granted concurrent access to a data item through the use of an optimistic concurrency algorithm . each transaction gets its own instance of the data item , such as in a cache or in an entity bean , such that it is not necessary to lock the data . the instances can come from the data or from other instances . when a transaction updates the data item , the optimistic concurrency algorithm ensures that the other instances are notified that the data item has been changed and that it is necessary to read a new instance , from the database or from an updated instance . this description is not intended to be a complete description of , or limit the scope of , the invention . other features , aspects , and objects of the invention can be obtained from a review of the specification , the figures , and the claims .