New concurrency semantics in DB2


Many users access and change data in a relational database, the database manager must allow users to make these changes while ensuring that data integrity is preserved. In earlier DB2 versions, Cursor Stability (CS) isolation level prevented an application from reading any row that was changed by other applications until the change was committed. This causes Writers to block readers and Readers may block writers.

DB2 9.7 offers a new currently committed semantics to significantly improve concurrency. With the enhancement, Writers do not block readers and Readers do not block writers.

Prior to DB2 9.7 Blocks -> Readers Writers
Cursor Stability Isolation Readers NO MAY BE
Writers YES YES

In DB2 9.7 Blocks -> Readers Writers
Cursor Stability Isolation Readers NO NO
Writers NO YES


The currently committed behavior is controlled by the database configuration parameter CUR_COMMIT. You can find out the setting of the parameter from TE, go to View > Configuration > DB Config.