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Drive Contains Large Number of Very Long Pathnames After Using Robocopy

If you use the Robocopy command in Windows Vista, the target drive may contain a large number of very long paths which cannot be deleted. The Robocopy command will also create many more files than exist on the source drive.

This occurs because Windows Vista changes many of the standard profile folders (eg. from C:\Documents and Settings to C:\Users) and to maintain compatibility with older applications which may have these paths hard-coded into them (as opposed to reading the correct folder from the registry), a number of junction points are added to the file system.

A junction point is a pointer to another location which looks like a directory. For example, you may create a junction point called C:\Data01 which points to C:\Apps\Database\Data01. Any access of the former will automatically reference the latter. Junction points can be very useful, but also dangerous and non-intuitive and should be used sparingly.

The particular problem that creates very long pathnames is that Windows Vista creates a recursive folder in each user profile by inserting a junction point which refers to its parent folder, and so any browsing through this junction point will continue forever as it simply keeps pointing back to itself.

When you use Robocopy to copy files, Robocopy traverses the junction points and, instead of recreating the junction point on the target, makes physical copies of all the files under the different path, resulting in many copies of the same file in different locations. When Robocopy traverses the recursive junction point, it keeps going until the path name exceeds the maximum allowed by the file system. However, the maximum allowed by the file system is much greater than that allowed by the shell (Windows Explorer) or the command processor (CMD.EXE) and so the files cannot be deleted.

Robocopy provides an option which disables traversing junction points — /XJ — and it should be considered mandatory when using Robocopy on or with Windows Vista.

To remove very long paths, it is necessary to manually rename the offending folder names to the shortest available. For example, if you have a path that contains many “\Application Data\Application Data\Application Data\Application Data\Application Data\Application Data\Application Data” etc, rename each “Application Data” folder to “a” and when finished the paths (“\a\a\a\a\a\a\a”) will be short enough to delete via Windows Explorer. You can also move the folders to another location to shorten the paths.

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