.. change::
    :tags: engine, usecase
    :tickets: 6342

    Generalized the :paramref:`_sa.create_engine.isolation_level` parameter to
    the base dialect so that it is no longer dependent on individual dialects
    to be present. This parameter sets up the "isolation level" setting to
    occur for all new database connections as soon as they are created by the
    connection pool, where the value then stays set without being reset on
    every checkin.

    The :paramref:`_sa.create_engine.isolation_level` parameter is essentially
    equivalent in functionality to using the
    :paramref:`_engine.Engine.execution_options.isolation_level` parameter via
    :meth:`_engine.Engine.execution_options` for an engine-wide setting. The
    difference is in that the former setting assigns the isolation level just
    once when a connection is created, the latter sets and resets the given
    level on each connection checkout.
