Active_IO=max-writes

    Specifies the maximum number of write operations to a backup
    device that the RMU Backup command will attempt simultaneously.
    This is not the maximum number of write operations in progress;
    that value is the product of active system I/O operations and the
    number of devices being written to simultaneously.

    The value of the
    Active_IO qualifier can range from 1 to 5. The default value
    is 3. Values larger than 3 can improve performance with some tape
    drives.