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OpenVMS Undocumented Features


This is the most complete collection of undocumented features we can find for OpenVMS. Some of these have been around since the time when it was called VMS while others are more current and have been added to OpenVMS V8.n. These features:

  • Are NOT documented (if they were, they wouldn't belong here)
  • Are NOT supported by PARSEC Group or HP
  • Are NOT guaranteed to work
  • May NOT exist in all versions of OpenVMS; past, present and future
  • Are subject to change, removal, enhancement or being documented at the whim of OpenVMS engineering
  • May be fun to know the next time you play OpenVMS trivial pursuit
  • May help you get your job done easier and faster
  • May help you impress your boss with your knowledge of the obscure

Data compression with BACKUP

The BACKUP utility has the ability to compress data it places in a saveset. This is enabled using the /DATA_FORMAT=COMPRESS qualifier.

$ directory /size /total *.com

Directory $22$DKA300:[WILLIAMS]

Total of 82 files, 6983 blocks.
$ backup *.com my_com.bck /save
$ backup *.com my_com_compressed.bck /save /data_format=compress
%BACKUP-I-COMPRESS, data compressed by 83%
$ directory /size my_com*.bck

Directory $22$DKA300:[WILLIAMS]

MY_COM.BCK;1                                 7938   9-MAY-2007 14:13:38.07
MY_COM_COMPRESSED.BCK;1                      1410   9-MAY-2007 14:14:30.22

Total of 2 files, 9348 blocks.

Fixing file attributes on BACKUP savesets

The /REPAIR qualifier to the BACKUP command will fix the characteristics of a backup save set. In the example, a backup saveset was copied to another node using FTP in binary mode. This corrupted the file characteristics of the saveset. The /REPAIR qualifier was used to repair this.

$ backup/list x.bck/save_set
Listing of save set(s)

%BACKUP-E-POSERROR, error positioning $22$DKA300:[WILLIAMS]X.BCK;3
-RMS-F-IOP, operation invalid for file organization or device
%BACKUP-E-READERRS, excessive error rate reading $22$DKA300:[WILLIAMS]X.BCK;3
-BACKUP-E-BLOCKCRC, software block CRC error
%BACKUP-I-OPERSPEC
%BACKUP-I-OPERASSIST, operator assistance has been requested
 Interrupt

$ backup/list x.bck/save_set/repair
Listing of save set(s)

%BACKUP-I-REPAIRED, saveset attributes changed to RFM=FIX, MRS=32256
Save set:          X.BCK
Written by:        WILLIAMS
UIC:               [000007,000006]
Date:               9-JUL-2007 10:55:42.63
Command:           BACK LOGIN.COM X.BCK/SAVE
Operating system:  OpenVMS Alpha version V8.3
BACKUP version:    V8.3
CPU ID register:   80000000
Node name:         _CLASS2::
Written on:        _$22$DKA300:
Block size:        32256
Group size:        10
Buffer count:      1238

[WILLIAMS]LOGIN.COM;56                                      4  30-APR-2007 16:00

Total of 1 file, 4 blocks
End of save set

Format argument to F$DELTA_TIME

The F$DELTA_TIME lexical function accepts two absolute time values and returns as a delta time the difference between them. A third, undocumented, argument to the function determines the formating of the returned value. Specifying, or defaulting, the format to ASCTIM causes the delta time to returned in a standard delta time format of dddd hh:mm:ss.cc. Specifying the format of DCL causes the time to be returned in a format that is acceptible in DCL commands, dddd-hh:mm:ss.cc with leading spaces removed.

$ write sys$output f$delta_time ("boot", "login")
   9 19:14:38.86
$ write sys$output f$delta_time ("boot", "login", "asctim")
   9 19:14:38.86
$ write sys$output f$delta_time ("boot", "login", "dcl")
9-19:14:38.86


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Please enjoy these features at your own risk. If you are aware of other features in OpenVMS which are currently undocumented, you may use our inquiry form to inform us. We may then add it to our list.