Thou shalt accept concurrent users
With respect to the management of multiple users concurrently interacting
with the system, the system should offer the same level of service as
current database systems provide.
It should therefore insure harmonious coexistence among users
working
simultaneously on the database. The system should therefore support
the standard notion of atomicity of a sequence of operations and of
controlled sharing. Serializability of operations should at least
be offered, although less strict alternatives may be offerered.