Grants (or denies) this role access to this schema.
access may be "all", "all_dimensions", "custom"
If access is "all_dimensions", the role has access
to all dimensions but still needs explicit access to cubes.
If access is "custom", no access will be inherited by
cubes for which no explicit rule is set.
If access is "all_dimensions", an implicut access is
given to all dimensions of the schema's cubes, provided the cube's
access attribute is either "custom" or "all".