Access intent -- isolation levels and update locks

The combination of concurrency and access type determines the isolation level for the persistence manager. The actual isolation level depends upon the particular database, as shown in the following table.

AccessIntent profile	Isolation level						For Update
DB2	Oracle*	SyBase	Informix	Cloudscape	SQL Server
wsPessimisticUpdate- Weakest LockAtLoad (Default policy)	RR	RC	RR	RR	RR	RR	No (*Oracle, Yes)
wsPessimisticUpdate	RR	RC	RR	RR	RR	RR	Yes
wsPessimisticRead	RR	RC	RR	RR	RR	RR	No
wsOptimisticUpdate	RC	RC	RC	RC	RC	RC	No
wsOptimisticRead	RC	RC	RC	RC	RC	RC	No
wsPessimisticUpdateNo-Collisions	RC	RC	RC	RC	RC	RC	No
wsPessimisticUpdate- Exclusive	S	S	S	S	S	S	Yes

• RC = JDBC Read committed

• RR = JDBC Repeatable read

• S = JDBC Serializable

• * Note: Oracle does not support JDBC Repeatable Read (RR). Therefore, wsPessimisticUpdate-weakestLockAtLoad and wsPessimisticUpdate behave the same way on Oracle as do wsPessismisticRead and wsOptimisticRead. Because of an Oracle restriction, the OracleXADataSource JDBC class cannot run with an S transaction isolation level. So you cannot use this class to run an application containing enterprise beans whose access intent policies are configured to cause the bean to load with RR isolation.

 

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