Tuning locking performance

Pessimistic locking strategy

Use the pessimistic locking strategy for read and write map operations where keys often collide. The pessimistic locking strategy has the greatest impact on performance.

Read committed and read uncommitted transaction isolation

When you are using pessimistic locking strategy, set the transaction isolation level with the Session.setTransactionIsolation method. For read committed or read uncommitted isolation, use the Session.TRANSACTION_READ_COMMITTED or Session.TRANSACTION_READ_UNCOMMITTED arguments depending on the isolation. To reset the transaction isolation level to the default pessimistic locking behavior, use the Session.setTransactionIsolation method with the Session.REPEATABLE_READ argument.

Read committed isolation reduces the duration of shared locks, which can improve concurrency and reduce the chance for deadlocks. This isolation level should be used when a transaction does not need assurances that read values remain unchanged for the duration of the transaction.

Use an uncommitted read when the transaction does not need to see the committed data.

Optimistic locking strategy

Optimistic locking is the default configuration. This strategy improves both performance and scalability compared to the pessimistic strategy. Use this strategy when your applications can tolerate some optimistic update failures, while still performing better than the pessimistic strategy. This strategy is excellent for read operations and infrequent update applications.

Tip: When you use optimistic locking, use the NoVersioningOptimisticCallback setting, if you do not need version checking. If you are not concerned about a potential collision, where two threads modify a value at the same time, then use this setting to disable versioning and consequently, decrease processor usage.

OptimisticCallback plug-in

The optimistic locking strategy makes a copy of the cache entries and compares them as needed. This operation can be expensive because copying the entry might involve cloning or serialization. To implement the fastest possible performance, implement the custom plug-in for non-entity maps.

Use version fields for entities

When you are using optimistic locking with entities, use the @Version annotation or the equivalent attribute in the Entity metadata descriptor file. The version annotation gives the ObjectGrid a very efficient way of tracking the version of an object. If the entity does not have a version field and optimistic locking is used for the entity, then the entire entity must be copied and compared.

None locking strategy

Use the none locking strategy for applications that are read only. The none locking strategy does not obtain any locks or use a lock manager. Therefore, this strategy offers the most concurrency, performance and scalability.