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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

Debug information from SHOW DEVICE command

Defining the SHOW$DEBUG logical name to 1 or TRUE causes the SHOW DEVICE command to display information about locks associated with the device. Defining the SHOW$DEBUG_LCKBUF logical name in addition to the SHOW$DEBUG logical name causes the raw data from the lock buffer to be dumped in ASCII and Hex format. The information may wrap for terminals with a width less than 132 columns.

$ define show$debug 1
$ define show$debug_lckbuf 1
$ show device sys$sysdevice

Locks queued to device lock "SYS$_$22$DKA300:":

   - Lock 3A0000C6,  length of items 00180078,  $ENQ status 00000001, value block F8C7F9A1 00000000 00000000 00000019
   -   LOCKID     PID      SYSID   (node)     REMLKID  REMSYSID           RQMODE  GRMODE   STATE
   -  6E000589  00000000  000100C4 (CLASS8)  02000180  000100CE (CLASS2)    01      01     01     [ CR / CR / GRANTED ]
   -  19000C38  00000000  000100C4 (CLASS8)  13000123  000100CB (YIPPIE)    01      01     01     [ CR / CR / GRANTED ]
   -  1900043D  00000000  000100C4 (CLASS8)  01000230  000100CA (CLASS9)    01      01     01     [ CR / CR / GRANTED ]
   -  010000D7  00000000  000100C4 (CLASS8)  010000D7  000100C4 (CLASS8)    01      01     01     [ CR / CR / GRANTED ]
   -  3A001103  39C003BD  000100C4 (CLASS8)  3A0000C6  000100CE (CLASS2)    00      00     01     [ NL / NL / GRANTED ]

   - Formatted dump of LKI$_LOCKS buffer:
   -   00000000 19000C38 000100CE 02000180 00010101 000100C4 00000000 6E000589 ...n....Ä...........Î...8....... 0000
   -   00010101 000100C4 00000000 1900043D 000100CB 13000123 00010101 000100C4 Ä.......#...Ë...=.......Ä....... 0020
   -   000100C4 010000D7 00010101 000100C4 00000000 010000D7 000100CA 01000230 0...Ê...×.......Ä.......×...Ä... 0040
   -   00000000 00000000 000100CE 3A0000C6 00010000 000100C4 39C003BD 3A001103 ...:½.À9Ä.......Æ..:Î........... 0060

Device                  Device           Error    Volume         Free  Trans Mnt
 Name                   Status           Count     Label        Blocks Count Cnt
$22$DKA300:   (CLASS2)  Mounted              0  ALPHA83CLS     2018765   585   4

Setting process quotas for the Audit Server process

By defining any of the following logical names in executive mode before starting the Audit Server process, it is possible to set the related quotas for that process. If the Audit Server has already been started, then it must be stopped and restarted for the changes to take effect.

  • AUDSRV$ASTLM - AST limit - default 200
  • AUDSRV$BIOLM - Buffered I/O limit - default 200
  • AUDSRV$BYTLM - Buffered I/O byte limit - default 100000
  • AUDSRV$DIOLM - Direct I/O limit - default 200
  • AUDSRV$ENQLM - ENQ limit - default 1000
  • AUDSRV$PGFLQUOTA - Page file quota - default 20480
  • AUDSRV$PRCLM - Process limit - default 10
  • AUDSRV$WSDEFAULT - Working set default - default 150
  • AUDSRV$WSQUOTA - Working set quota - default 250
  • AUDSRV$WSEXTENT - Working set extent - default 2048

SHOW PATH command

The SHOW PATH /DEVICE command displays information about a specific path to multi-pathed devices. Adding the /FULL qualifier provides more detailed information, including the status of the last check of the path.

$ show device /multipath
Device                  Device           Error         Current
 Name                   Status           Count  Paths    path
$100$DKA0:    (VMSPR1)  Mounted              4   2/ 2  PKA0.0
$100$DKA1:    (VMSPR1)  Mounted             73   2/ 2  PKA0.0
$100$DKA4:    (VMSPR1)  Online               0   2/ 2  PKA0.0
$ show path/device pka0.0

Path                         Path       Cur      Tot        Last Transition
Name                         Status     Dev Cnt  Dev Cnt    of Availability
PKA0.0                       Available     3       3    14-MAY-2007 07:17:24.35
$ show path/device pka0.0/full

Path: PKA0.0
    Status1: 00000505 path_available,normal_timer,enabled_found,polling_started
    Status2: 00000001 polling_enabled

    Current UCB count:        3
    Devices on path:          3

    Time of last transition: 14-MAY-2007 07:17:24.35
    Time user disabled:      None

    UCB used for polling:    81D2BDC0 (_$100$DKA0:)
    poller TQE due time:      9-JUL-2007 08:57:24.47
    Poller IRP iost1:        00000C7B                 Poller IRP iost2: 00000080
$ write sys$output f$message (%xc7b)
%SYSTEM-I-DEVCON, device is connected on path


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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.