A database or some portion thereof is partitioned into ownership groups.
Each ownership group is assigned one or more database servers as owners of
the ownership group. The database servers that are assigned as owners of
an ownership group are treated as the owners of all data items that belong
to the ownership group. That is, they are allowed to directly access the
data items within the ownership group, while other database servers are
not allowed to directly access those data items. A mechanism is provided
for transitioning ownership of a data item. Ownership is transferred by
disabling access to the data item, waiting for all transactions that have
made changes to the data item to either commit or abort, changing data
that indicates ownership of the data item from a first owner to a second
owner, and enabling access to the data item.