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

       /CRC (default)
       /NOCRC

    Input or Output Save-Set Qualifier

    As an input save-set qualifier, /CRC causes the software cyclic
    redundancy check (CRC) encoded in the save set's data blocks
    to be checked (/CRC) or ignored (/NOCRC). If you ignore the CRC
    encoding, you reduce processing time at the risk of increasing
    data error.

    As an output save-set qualifier, /CRC specifies that software
    CRC checking code is to be computed and stored in the data blocks
    of the output save set. To disable CRC checking, use the /NOCRC
    qualifier.