Multiple concurrency levels

Derby supports the SERIALIZABLE (RR), REPEATABLE (RS), READ COMMITTED (CS), and READ UNCOMMITTED (UR) isolation levels.

CS (the default isolation level) provides the best balance between concurrency and consistency in multiple-client environments.
RS provides less consistency than RR but allows more concurrency.
RR provides greatest consistency.
UR provides maximum concurrency, if uncommitted values are allowed in the query. It is typically used if approximate results are acceptable.

See "Types and Scope of Locks in Derby Systems" in the Derby Developer's Guide for more information.

Related concepts
Row-level locking
Multi-connection and multi-threading
Administrative tools