Enables only the modes specified, disabling all other previously
    defined modes. For example, if a database is to be used for read-
    only access and you want to disable all other transaction modes,
    use the following statement:

    SQL> CREATE DATABASE FILENAME mf_personnel
    cont>   SET TRANSACTION MODES (READ ONLY);

    If not specified, the default transaction mode is ALL.

    Specifying a negated transaction mode or specifying NONE disables
    all transaction usage. Disabling all transaction usage would be
    useful when, for example, you want to perform major restructuring
    of the physical database. Execute the ALTER DATABASE statement
    to re-enable transaction modes or use Oracle RMU, the Oracle Rdb
    management utility.