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XXCOPY
Version
3.33.3


Released
2016-10-28
©2016 Copyright
Pixelab

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    XXCOPY TECHNICAL BULLETIN #021

    From:    Kan Yabumoto           tech@xxcopy.com
    To:      XXCOPY user
    Subject: XXCOPY in a network environment
    Date:    2000-11-14
    ===============================================================================
    
    While XXCOPY is useful in a stand-alone PC, it is widely used in
    network environments.  Since the default settings of various XXCOPY
    operations are designed primarily for copying local drives, you
    need to pay special attentions when you operate XXCOPY in a
    network environment.
    
    In this article, the following XXCOPY command switches are examined
    specifically with networked environments in mind.
    
       /NX0    Disables the shortname preservation feature
       /FF     Tolerates up to 2-second difference in time comparison
       /CK0    Disables pre-checking of the remaining space
       /FU     Selects universal time (UNC) for file time
    
    
    1.  The Shortname preservation.
    
          One of the reasons XXCOPY enjoys its popularity among freeware
          users is the shortname preservation feature.  While this
          feature is essential to ensure a proper duplication of the
          system drive, the feature may not work (and even becomes a
          detriment) in some networked environment with mixed Operating
          Systems (or file systems) where the source and the destination
          volumes are of different type in file system.  It is best if
          you test whether the shortname-preserving feature is working
          for you on your particular environment.
    
          Since shortname preservation feature requires XXCOPY to
          issue a sequence of system calls for renaming, it is a
          time consuming operation especially when it fails.  If your
          XXCOPY exhibits an inordinately low performance, you should
          suspect this feature as the likely cause of the trouble.
          In that case, just add  /NX0 to disable the feature (giving
          up the idea of preserving the shortname).  For example,
          it would be futile for XXCOPY to save the shortname while
          the underlying OS (e.g, Linux) does not even support it.
    
          XXCOPY sets the /NX switch on a local drive copy.  And, if
          either the source or the destination is specified by an UNC
          (starting with two backslashes.  E.g,  \\myserver\cdrive\),
          the /NX0 is used as the default setting.  If you assert your
          desire by an explicit /NX switch, the switch will be honored.
    
          Unfortunately, it is not always easy for XXCOPY to determine
          whether the combination of the source and the destination is
          suitable for the /NX operation, an explicit command switch
          of /NX and /NX0 should work the best.
    
           -----------------------------------------------------------
            Starting with v2.43.x, the shortname preservation feature
            is disabled by an UNC specifier either on src or dst.
    
            Due to Microsoft' XCOPY added their /N switch in recent
            Windows 9x release, XXCOPY's shortname preservation
            feature is no longer assigned to /N.  Starting with
            v2.42.0, it is controlled by /NX and /NX0.  We regret
            that this change forced us to broke existing batch files.
           -----------------------------------------------------------
    
          See article: XXTB #03, for related topics.
    
    
    2.  Time stamp granularity.
    
          Different file systems use different ways to keep track of
          the date and time information associated with a file.  When
          you use XXCOPY to transfer files from one file system to another,
          you should be aware of the characteristics of the file system.
          The granularity of the file time maintained by the OS is the
          first one to note:
    
                File System             File time granularity
               -----------------------------------------------
                FAT12/FAT16/FAT32            2 sec
                NTFS                       100 nsec
                Unix/Linux                   1 sec
    
          If your XXCOPY operation does not check the file time as the
          criteria for file selection, the granularity is not an issue.
          However, when you use an operation which involves the file time,
          you should know more.  The following list shows the switches
          which depend on the time stamp of the file.
    
              /BI     Backup Incremental
              /BN     Backup Newer files
              /Bo     Backup Older files
              /BS     Backup Same-time/size files
              /BX     Backup Different-time/size files
              /BU     Backup (combination using /BI)
              /DA     Copies Newer files
              /DB     Copies Older files
              /DS     Copies Same-time files
              /DX     Copies Different-time files
              /CLONE  Backup (combination using /BI)
    
          The best way to handle such a case with mixed file systems is
          to use the /FF (Fuzzy Filetime) switch.  With the switch, XXCOPY
          will ignore the difference in filetime values for up to 2 seconds
          to accommodate the granularity difference in file time among
          various file systems.
    
    3.  Remaining space check.
    
          Ideally speaking, a file copy utility should know the remaining
          space on the destination before a copy operation is started.
          That is exactly what XXCOPY does.  However, when the destination
          directory is on a remote machine, the value XXCOPY receives as
          the remaining space from the Operating system is sometimes
          not accurate.  When this happens, XXCOPY terminates the current
          session and returns the "Disk Full" error condition.
    
          Many users have reported that XXCOPY prematurely terminates
          a session due to a false reading on the remaining space.  That
          is, XXCOPY's idealistic design backfires --- and the more
          primitive design (e.g., the COPY command) works better by not
          checking the remaining space.  So, you can override XXCOPY's
          pre-check feature by /CK0  (default is /CK).
    
    
    4.  Time stamp type, and locality .
    
          The original FAT12 and FAT16 file systems used by DOS had only
          one type of file time which represents the last-modified time.
          The FAT32 and NTFS maintain three types of time stamps for each
          file.
    
              Time when the file was Last-modified  (/FW  default)
              Time when the file was First-created  (/FC)
              Time when the file was Last-accessed  (/FA)
    
          By default, XXCOPY uses the Last-modified value as the file
          time (/FW).
    
          The file time is referenced either by the local time or by the
          universal time (UTC, also known as GMT).  The default setting
          uses the local time since most of us eat lunch at Noon(?).
          The setting is either /FL (Local, default) and /FU (UTC).
    
    
          Since we do not hear much problems associated with the
          time-representation aspects, we assume this is not a serious
          issue with XXCOPY.  But, XXCOPY is prepared to deal with it.
    
          See article: XXTB #15, for related topics.
    
    
    5.  Conclusion
    
          In this article, a few solutions are provided to alleviate
          common problems dealing with XXCOPY operation across networked
          drives.  The solutions listed here generally works.  However,
          they are only a guideline and your case may involve other
          factors which are overlooked in this article.
    
          Please note that this article does not cover all common pitfalls.
          We welcome your feedback when you encounter similar problems
          which we have not yet addressed.
    
    
    Please send E-Mail to <tech@xxcopy.com>..
    
    
    
    
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