The feature I am describing today is one of the smaller items (marketing-wise) on the "new in DB2 9.7" list. However, it is important for day-to-day operations and it is trickier to implement (why else did it take until 9.7?). The enhancement is that now concurrent transactions with insert, update, and delete operations are allowed parallel to a XML index creation or REORGanization.
In earlier release with pureXML functionality only read access was possible which required some kind of workload planning to creating new indexes. With the improvement the index building process will catch up with ongoing IUD activities and only will require exclusive access, i.e., blocking other activities, during that time. This is the same behavior as for non-XML indexes (see CREATE INDEX for details).