Syntax options:

    MULTISCHEMA IS ON | MULTISCHEMA IS OFF

    The MULTISCHEMA IS ON clause enables multischema naming for the
    duration of the database attach. The MULTISCHEMA IS OFF clause
    disables multischema naming for the duration of the database
    attach. On attach, multischema naming defaults to the setting
    specified during database definition.

    You can use multischema naming only when attached to a database
    that was created with the multischema attribute. If you specify
    the MULTISCHEMA IS ON clause with a database that was not created
    with the multischema attribute, SQL returns an error message, as
    shown in the following example:

    SQL> ATTACH 'ALIAS PERS_ALIAS FILENAME personnel MULTISCHEMA IS ON';
    %SQL-F-NOPHYSMULSCH, The physical multischema attribute was not specified for
    the database