Attempts to update the following attributes in the header of
    the file: longest record length (LRL) and/or file length hint
    attribute.

    You must use this qualifier in combination with either
    /STATISTICS or /CHECK (the default).

    This qualifier only applies to sequential file organizations and
    is ignored for any other file organization. The /UPDATE_HEADER
    qualifier attempts to update the LRL and/or file hint attribute
    in the file header if the calculated value(s) differ from the
    current value(s) in the file header. The /UPDATE_HEADER qualifier
    applies to:

    o  An LRL request - if the file is sequential and has a record
       format other than undefined (UDF).

    o  A HINT request - if the file is sequential, the record format
       is either variable (VAR) or variable with fixed control (VFC),
       and the file is located on an ODS-5 disk device.

    It is not supported for remote accesses; requests are ignored.

    The /UPDATE_HEADER qualifier requires either the STATISTICS or
    CHECK (default) functions since calculating new values for the
    LRL and/or file length hint presumes that all the records in the
    sequential file are processed. It is not compatible with the /FDL
    qualifier, the /INTERACTIVE qualifier, or the /SUMMARY qualifier.

    Any errors returned by the file system when an attempt to update
    the file header fails are ignored. If the update succeeds, the
    updated values are displayed at the end of the report.