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JPA 2 supports both optimistic locking and pessimistic locking. Locking is essential to avoid update collisions resulting from simultaneous updates to the same data by two concurrent users. Locking in ObjectDB (and in JPA) is always at the database object level

.EntityManagervoid lock(  Object entity,   ) Lock an entity instance that is contained in the persistence context with the specified lock mode type

.EntityManagervoid lock(  Object entity,    Lock an entity instance that is contained in the persistence context with the specified lock mode type. If a pessimistic lock mode type is specified and the entity contains

. Lock Mode (setLockMode) ObjectDB uses automatic lock#optimistic_locking">optimistic locking to prevent concurrent changes to entity objects by multiple users. JPA 2 adds support for lock#pessimistic_locking">pessimistic

> Locking Automatic object versioning (can be injected to a @Version field). lock#optimistic_locking">Optimistic locking (always active). Implicit pessimistic locking (JDO

;lockMode) Find by primary key and lock. Find by primary key and lock. Search for an entity of the specified class and primary key and lock it with respect to the specified lock type. If the entity instance is contained in

="write" /> <locking version-check="true" /> <processing cache="64mb" max-threads="10 ... >"all" is used. The <locking> element <locking ... ;locking> element specifies if optimistic locking is enabled. Optimistic locking is completely

()) tr.rollback(); if (!pm.isClosed()) pm.close(); } Automatic Lock Management ObjectDB manages an automatic lock mechanism in order to prevent a database object ... from the database a READ lock on that object is obtained by the PersistenceManager

of obj has been modified. Object States and Locks As explained in section 5.3, ObjectDB manages an automatic lock ... in ObjectDB), there is a strong relationship between object states and object locks.

;lockMode)Find by primary key and lock.Find by primary key and lock. Search for an entity of the specified class and primary key and lock it with respect to the specified lock type. If the entity instance is contained in