DB2 Viper 2's support for optimistic locking strategies includes two core pieces:

1. Automatic time stamping or change marking of rows as they are modified in the database.
2. Two new functions RID() and RID_BIT() that externalize the physical position of a row.

While some may disapprove of exposing physical properties of a row through SQL, it is undeniable that RID() and RID_BIT() make porting of applications that use ROWID a lot easier.


https://publib.boulder.ibm.com/infocenter/db2luw/v9r5/index.jsp