An access intent policy is a named set of properties or access intents that govern data access for Enterprise JavaBeans (EJB) persistence. You can assign policies to an entity bean and to individual methods on an entity bean's home, remote, or local interfaces during assembly. You can set access intents only within EJB Version 2.x-compliant and later modules for entity beans with CMP Version 2.x.
This product supplies a number of access intent policies that specify permutations of read intent and concurrency control; the pessimistic and update policy can be qualified further. The selected policy determines the appropriate isolation level and locking strategy used by the run time environment.
You can use application profiling or method level access intent policies to control access intent more precisely. Method-level access intent policies are named and defined at the module level. A module can have one or many policies. Policies are assigned, and apply, to individual methods of the declared interfaces of entity beans and their associated home interfaces. A method-based policy is acted upon by the combination of the EJB container and persistence manager when the method causes the entity to load.
For entity beans that are backed by tables with nullable columns, use an optimistic policy with caution. The top down default mapping excludes nullable fields. You can override this when doing a meet-in-the-middle mapping. The fields used in overqualified updates are specified in the ejb-rdb mapping. If nullable columns are selected as overqualified columns, partial update should also be selected.
An entity that is configured with a read-only policy that causes a bean to be activated can cause problems if updates are attempted within the same transaction. Those changes are not committed, and the process displays an exception because data integrity might be compromised.