VM Backups and Archives

The phaseout of the VM system marks a significant transition point in the computing infrastructure for the Lab and serves as a time for examination of many policies developed for mainframe-style computing. The era of distributed computing has substantially altered the cost and resource tradeoffs; one such area affecting many computing users is archive and backup. While it is too early to announce a radical change in those policies (it will take some months to develop the full plan in conjunction with interested users), preliminary discussions within SCS underscored the need to clarify the current and future access to archive and backup data associated with the VM system. Since the VM system is currently scheduled to be shut down in May, 1998, this note serves as a warning concerning the schedule on which certain data will no longer be accessible.


All media have limited lifespan and all data storage technologies have limited windows of cost effectiveness. The probability of successfully retrieving data from offline media diminishes over time and becomes fairly small at a time period of, say, ten years unless extraordinary measures are taken.

Additionally, hardware technology advances causing it to be impossible to recover data even from well-maintained media. Data stored in particular formats also may create problems as the hardware and software can no longer make sense of it. Examples of current data format problems include binary floating point data stored on the VM system, COPYFILE packed format for data used by various CMS commands, and backups performed in a device-dependent fashion.

These limitations have led us to review policies relating to backups and archives. What follows relates to data from the VM mainframe system, but these limitations will also be a strong factor in new archive and backup policies being developed for Unix and Windows NT systems.

VM Backups

Backups prior to April,1989 (tape reels)

Existing backup reels will be retained until the shutdown of the VM system, at which time the reels will be destroyed.

Backups since April,1989 (cartridges)

Existing backup cartridges will be retained until the shutdown of the VM system, at which time the cartridges will be recycled or destroyed, depending on their age and condition.

VM Archives

Archives made through April 10, 1989 (tape reels)

Our recent experience has been that the tape media have degraded, and that this data may not be recoverable from archive tapes. Hardware to read tape reels is limited and is fragile due to its age and limited availability of parts. Of course, the poor condition of the tapes creates further problems for the reliability of the hardware.

Until VM is shut down, we will make a best effort attempt to recover data from these tapes, within the constraints of our limited staff and hardware resources. Users should be aware the probability of successful recovery is low.

Archives since April 10, 1989 (cartridges)

SCS has some rudimentary Unix tools which can be used to recover data from VM archive tapes. These tools will produce the most satisfactory results on files which were originally in a standard CMS text file format (e.g. program source, listings, memos). Binary files, COPYFILE packed format files, and OS Simulation (CMS mode 4) files will be much more problematic to convert to a usable form in Unix. SCS may have very limited consulting available to provide advice in data recovery.

Prior to the VM Phaseout, requests for recovery of data from archive cartridges will be easier to satisfy but may well require intervention of the tape librarian to place the correct cartridge in the silo. There are no current plans for the removal of cartridge tape drives or the software allowing the VM archive tapes to be read from Unix. Current plans are to retain the VM archive tape cartridges as long as it is feasible to read them with functioning hardware supported by current software (operating system and utilities).

VM Minidisks

VM accounts which have been individually deleted (usually by a group czar) have had their minidisks archived at that time. (This procedure has been followed for many years, not just for accounts closed during the VM Phaseout.)

For accounts deleted from VM in large groups, binary images of the minidisks are accessible in Unix in /nfs/morgue/group/userid, where group is your two-letter group code, and userid is your VM userid. Each minidisk belonging to the account will be a subdirectory. Files from VM are usually in EBCDIC code and need translation before being readable on UNIX. The 'vmfile' command will translate EBCDIC to ASCII and convert VM record conventions to UNIX conventions.


The Workstation Data Save Facility (WDSF), which used the VM system for its data storage server, is being replaced by the Adstar Distributed Storage Manager (ADSM), which uses a Unix data storage server. More information about this replacement will be available soon. Files archived with WDSF are expected to be converted so they are recoverable using ADSM.

What Do You Do?

Data stored on ("round") tape reels, including data archived on VM through April 10, 1989, must be retrieved before VM goes away, now scheduled for late May of this year.  Files archived on ("square") tape cartridges -- starting April 10, 1989 -- will remain accessible through Unix, but it is FAR easier to restore them now.

To obtain a list of files archived from VM onto tape:

SCS will retrieve critical files from archive tapes for a $50 charge per tape processed to partially recover costs of retrieving the tapes and maintaining the drives. Due to the condition of the tape media and drives, there is no guarantee of successful recovery of the data, even with the best efforts of the staff.  If you wish SCS to perform the file recovery, fill out the Archive Request form.

If you have any questions or comments on this information, please send email to archive-admin@slac.stanford.edu

Page Owner: Bob Cowles