WebSphere® Application Server delivers container-managed persistence (CMP) services beyond the standards set by the Enterprise JavaBeans (EJB) specification.
The use of inheritance enables a developer to define fields, relationships, and business logic in a superclass entity bean that are inherited by all subclasses. See the section EJB inheritance of the Rational® Application Developer documentation for details on using inheritance with WebSphere Application Server and entity beans.
The use of preceding or following midnight to calculate a future time value depends on the value of LifetimeInCache. If LifetimeInCache plus preceding midnight is earlier than the current time, then the following midnight is used.
When you use the ClockTime setting, the value of LifetimeInCache must not represent more than 24 hours. If it does, the cache manager subtracts increments of 24 hours from it until a value less than or equal to 24 hours is achieved. To invalidate data at 12 midnight, you set LifetimeInCache to zero (0).
Because the data used by an entity bean can be loaded by previous transactions, if you configure the bean as LifeTimeInCache, the isolation level and update lock (access intent policies) for the bean are lost for the current transaction. This can cause data integrity problems if your application has logic to calculate information from read-only data, and then save the result in another bean. This makes it important to perform read-read consistency checking to ensure the data get locked properly if loading the data from in-memory cache; otherwise, data is updated to the database without knowing the underlining data is changed, causing previous changes to be lost. For more information, see the topic Configuring read-read consistency checking with an assembly tool.
To use this function, you declare the bean type as read-only by selecting a particular set of bean caching options, through a selection list within the assembly tooling. See Configuring read-read consistency checking with an assembly tool for details.