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DFU (Disk / File Utilities) is a tool developed to help finding and solving disk, directory and file problems on the OpenVMS operating system. The usage of low-level VMS-I/O features have resulted in a powerful and high-performance utility. Also, DFU provides many features which are not available with standard DCL commands.

DFU supports all types of disk sets which comply to the OpenVMS ODS-2 and ODS-5 standard, such as volume sets, stripe sets, shadow sets and RAID sets, and combinations of these.

The current release is V3.2, and you can get it here (pcsi) or here (zip). Notice that this kit will install on OpenVMS Alpha, starting at V7.3-1, and OpenVMS I64 starting at V8.2. OpenVMS VAX is not supported. So there are no more separate kits for Alpha and Ia64 as before. Make sure you uninstall any old version (PRODUCT REMOVE DFU) before installing this one.

The V3.2 documentation can be downloaded here (pdf).


DFU is freeware. It may be freely downloaded and used. The sources are not available, and support is limited. But in case of problems report them here and they may get fixed. We are not responsible for any malfunction or data loss caused by this software.

Problem on VMS versions older than V7.3-2:

There is a problem with DFU V3.2 on VMS version V7.3-1 that will generate a BADPARAM error. This will probably fixed in a future version, for now it is recommended to install an older version of DFU (V3.1).


This version of DFU offers only bugfixes. The list below gives the changes since DFU version V3.1-1 :

Workaround for ACCVIO in REPORT and VERIFY.
Under rare circumstances, accessing the BITMAP.SYS file may cause an ACCVIO. This is a compiler issue (only on Alpha), but DFU now has a workaround which solves it.

SEARCH .../SINCE and /BEFORE does not correctly report files.
The way DFU did file date compares was not accurate and could be off by a few minutes. E.g. SEARCH/CREATED=SINCE=09:00 could report files with a creation date of 08:58. This problem is now fixed.

A wrong fileheader (file name was empty) caused a crash. Routine get_name returns a -1 length, but the file dsc$w_length is unsigned so the comparison with a -1 did not work. Changed it into 0xFFFF.

Fixed serious issue with VERIFY/REBUILD
Under rare circumstances we could get disk corruption.

Fix issues when logical volume size is smaller than device size (maxblocks)

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