Used to change any read/write storage area (except the RDB$SYSTEM
    storage area) to a read-only storage area.

    To change a read/write RDB$SYSTEM storage area to read-only, you
    must use the READ_ONLY option of the change-database-options2
    clause.

    You cannot change the parameters of a read-only storage area.
    You must first change the storage area to a read/write area, then
    change the parameters.

    Also, no write operation can be done in a read-only storage area
    except a cardinality update. See the RMU/ANALYZE/CARDINALITY help
    topic in the RMU help file for more information and restrictions
    on updating cardinalities.