/sys$common/syshlp/helplib.hlb INITIALIZE, Qualifiers, /DATA_CHECK  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /DATA_CHECK[=(option[,...])]

    Checks all read and write operations on the disk. By default,
    no data checks are made. Specify one or both of the following
    options:

    READ    Checks all read operations.

    WRITE   Checks all write operations; default if only the /DATA_
            CHECK qualifier is specified.

    To override the checking you specify at initialization for disks,
    enter a MOUNT command to mount the volume.