We have been implementing an isolation subsystem
prototype to further justify the cost-effectiveness of
Architecture II. In order to transparently isolate a
transaction on top of a commercial single-version DBMS
such as Oracle, we need to (a) use extra tables to simulate
multiple versions and (b) rewrite the SQL statements
involved in this transaction in such a way that the one-way
isolation policy can be achieved. Note that query rewriting
could cause some service delay to isolated users but not to
unisolated users.