The OpenVMS Frequently Asked Questions(FAQ)

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11.9 Why doesn't XtAppAddInput() work on OpenVMS?

Yes, XtAppAddInput() does work on OpenVMS. The MIT definition of the X Windows call XtAppAddInput() includes platform-specific arguments.

On platforms where C is the typically the primary programming language for the platform, the file descriptor mask is one of the arguments to the XtAppAddInput() call.

On OpenVMS, the platform-specific arguments to this call include an event flag and an IOSB, as these are the traditional OpenVMS constructs used to synchronize the completion of asynchronous operations. While it would be easier to port non-OpenVMS C code that calls XtAppAddInput() over to OpenVMS if the arguments included the C file descriptor, this would make the call unusable from other OpenVMS languages, and would make it extremely difficult to use OpenVMS features such as ASTs and sys$qio calls.

One restriction on the event flag: the event flag chosen must be from event flag cluster zero. When using the traditional lib$get_ef and lib$free_ef calls to allocate and deallocate event flags, you must first explicitly call lib$free_ef to free up some event flags in event flag cluster zero. Please see the event flag documentation for specific details on these calls and for specific event flags that can be freed in event flag cluster zero.

Here is some example code that covers calling this routine on OpenVMS:

    m->InputID = XtAppAddInput( 
        the_callback, 1 ); 
    if ( !((int) m->InputID )) 
            "Can't Access Device", 
            (String *) NULL, 
            (Cardinal *) NULL ); 

11.10 Why do the keyboard arrow keys move the DECwindows cursor?

Congratulations, you have just stumbled into "dead rodent" mode. This DECwindows environment---where the keyboard arrow keys move the mouse cursor and where the [SELECT], [PREV], and [NEXT] keys emulate the three mouse buttons---allows rudimentary system operations when the mouse is among the casualties.

To enter or exit "dead rodent" mode, enter the following: [CTRL/SHIFT/F3]

11.11 Why does half my DECwindows display blank?

This is likely a result of receiving an OPCOM or other console message on a system that shares the system console with the DECwindows graphics workstation display.

You can toggle off the console display window using [CTRL/F2] and you can enable a serial console per Section 14.3.6 or Section

Also see the console message window application available with recent DECwindows versions---DECwindows versions V1.2-3 and later will enable this window by default. For details on this console message window, see the DECW$CONSOLE_SELECTION option in SYS$STARTUP:DECW$PRIVATE_APPS_SETUP.TEMPLATE.

On older releases, you can disable output using the following:


Also see Section, Section 14.19, and Also see Section 8.3,

11.12 %DECW-W-NODEVICE, No graphics device found on this system?

To resolve the following error:

%DECW-W-NODEVICE, No graphics device found on this system 
-DECW-I-NODECW, DECwindows graphics drivers will not be loaded 

Also see Section 11.6.

11.13 How can I reset the warning bell volume?

With DECwindows CDE drivers and ECOs starting with ECOs for the DECwindows keyboard driver SYS$IKBDRIVER.EXE in OpenVMS Alpha V7.1-2 and V7.2-1 and with the SYS$IKBDRIVER.EXE included in OpenVMS V7.2-1H1 and later, the DECwindows CDE controls will now correctly manage the setting of the warning bell volume.

Unfortunately, the equivalent controls in the older DECwindows Motif interface are not compatible and can no longer manage the warning bell volume.

If you need to manage the volume with DECwindows Motif, consider using the following approach:

$ @decw$utils:decw$define_utils 
$ xset b 1 100 100 

The numerics are the volume, pitch, and duration, respectively.

Why? When OpenVMS first started supporting the PC-style keyboards, the X Windows Server and the keyboard driver interface did not support the pitch and duration, and neither did DECwindows Motif. The DECwindows keyboard driver was accordingly changed to use the volume from the keyclick setting (keyclick is not available in a PC-style keyboard) and the bell volume setting to control the pitch and duration.

DECwindows CDE does provide sliders for setting pitch and duration, so the keyboard driver and X Windows Server were modified to provide all of the information, and now the DECwindows CDE sliders work. This change is unfortunately incompatible with the old scheme used on the pre-CDE desktops, and the volume controls are now incompatible with the current keyboard drivers. Hence the use of xset.

11.14 How can I alter the DECwindows CDE backdrop?

To select a separate backdrop to be displayed on each screen using DECwindows CDE:

11.15 How can I enable the DECwindows TCP/IP Transport

To configure the TCP/IP transport for DECwindows, first ensure that a TCP/IP package is installed and configured. Then set the DCL symbol DECW$SERVER_TRANSPORTS in SYS$MANAGER:DECW$PRIVATE_SERVER_SETUP.COM to the appropriate local value, based on the comments in that file. If you do not have a copy of SYS$STARTUP:DECW$PRIVATE_SERVER_SETUP.COM, the use the following COPY command to create this file based on the provided template file:


Chapter 12
Miscellaneous Information

12.1 Where can I find information on escape and control sequences?

Information on escape and control sequences can be found in the OpenVMS I/O User's Reference Manual, in the chapter on the terminal driver. The chapter also includes details on the general format and content of these sequences.

Specific details on the escape and control sequences supported by a particular serial device are typically found in the documentation provided with the specific device. Information on the sequences supported by DECwindows DECterm terminal emulator are included in the DECwindows documentation.

Examples of common escape and control sequences---those typically used by the OpenVMS screen management package---can be found in the OpenVMS system file SYS$SYSTEM:SMGTERMS.TXT.

The following refers to the function keys on the LK-series keyboards found on the VT-series terminals such as the VT220 and VT510, and the LK-series keyboards found on the OpenVMS workstations, and the keyboards found on compatible terminals. (Though note that the keyboard itself does not generate the sequence, the terminal or terminal emulator generates the sequence in response to user input.) In the following, {CSI} is decimal code 155 and can be replaced by the sequence "{ESC}[" (without the quotes) particularly for seven-bit operations, SS3 is decimal code 143 and can be replaced by "{ESC}O" particularly for seven-bit operations. Older VT1xx series terminals and any other terminals operating with seven-bit characters should not be sent eight-bit operators such as {CSI} and {SS3}.

PF1={SS3}P PF2={SS3}Q PF3={SS3}R PF4={SS3}S 
KP0={SS3}p KP1={SS3}q KP2={SS3}r KP3={SS3}s KP4={SS3}t KP5={SS3}u 
KP6={SS3}v KP7={SS3}w KP8={SS3}x KP9={SS3}y KPCOMMA={SS3}l KPMINUS={SS3}m 
PREV={CSI}5~ NEXT={CSI}6~ F6={CSI}17~ F7={CSI}18~ F8={CSI}19~ F9={CSI}20~ 
F10={CSI}21~ F11={CSI}23~ F12={CSI}24~ F13={CSI}25~ F14={CSI}26~ 
HELP={CSI}28~ DO={CSI}29~ F17={CSI}31~ F18={CSI}32~ F19={CSI}33~ F20={CSI}34~ 

An example of working with escape sequences (in DCL) follows:

$ esc5m = "*[5m" 
$ esc5m[0,8] = 27 
$ esc0m = "*[0m" 
$ esc0m[0,8] = 27 
$ write sys$output esc5m + "blinking text" + esc0m 

Documentation on an ANSI terminal relatively similar to the VT525 series is available at:

Also see the various documentation and manuals available at:

Information on the ReGIS graphics character set is available at:


Also see Section 11.7, Section 8.11.

12.2 Does DECprint (DCPS) work with the LRA0 parallel port?

The parallel printing port LRA0: found on many OpenVMS Alpha systems is capable of some bidirectional communications, with enough for basic operations with most parallel printers.

DECprint (DCPS) requires more than just the simple handshaking provided by the LRA0: port, therefore DCPS does not work with the LRA0: port.

12.3 How do I check for free space on a (BACKUP) tape?

You cannot know for certain, though you can certainly estimate the remaining capacity.

Tape media is different than disk media, as disks have a known and pre-determined fixed capacity. Modern disks also appear logically perfect, based on bad block revectoring support and the extra blocks hidden within the disk structure for these bad block replacements.

The capacity of tape media is not nearly as pre-determined, and the capacity can vary across different tape media (slightly different media lengths or different foil markers or other variations, for instance) and even on the same media over time (as bad spots in the media arise). Tapes can vary the amount of recording media required, depending on the remaining length of the tape, the numbers of correctable and uncorrectable media errors that might occur, the numbers and sizes of the inter-record gaps and related tape structure overhead, the particular media error recovery chosen, the tape density, the efficiently of any data compression in use, and the storage overhead required by BACKUP, tar, and other similar commands.

BACKUP using with the default settings results in approximately 15% overhead, in terms of saveset size. (eg: Assuming a 500 KB input, the total size would be 575 KB.)

Assuming no compression:
4 GB media / 575 KB saveset = 7294 savesets

Assuming 1:2 compression:
8 GB media / 575 KB saveset = 14588 savesets

Note: There are no inter-record gaps on DAT tapes. (When determining media capacity, you have to consider these with nine-track magtape media. Not with DAT (DDS). However, the block structure underneath the variable length record recording is based on a block size of circa 124 KB. Further, writing doubles filemarks and such can cause a loss of up to the underlying block size. Thus even though there are no inter-record gaps on DAT, larger savesets are still usually best.

The compression algorithms used on various devices are generally not documented---further, there is no way to calculate the effective data compression ratio, the tape mark overhead, and similar given just the data to be stored on tape---short of actually trying it, of course.

A typical compression ratio found with "everyday" data is somewhere around 1:1.8 to 1:2.

Note: OpenVMS often uses the term COMPACTION for compression control, as in the qualifier /MEDIA_FORMAT=COMPACTION.

12.4 So what happened to sys$cmsuper?

There is no SYS$CMSUPR service.

The typical wisdom for getting into supervisor access mode (from user mode) is to execute a routine in executive mode (via a call to SYS$CMEXEC and the appropriate privilege) and then issue a SYS$DCLAST with the ASTADR parameter pointing to your routine entry point and the ACMODE parameter specified as PSL$C_SUPER.

Alternatively, you can reset mode in the call stack return path and unwind from executive or kernel out into supervisor mode.

12.5 Correctly using license PAKs and LMF?

If you have multiple LMF$LICENSE.LDB databases in your OpenVMS Cluster, then each and every PAK must be installed in each and every license database present in an OpenVMS Cluster. Even if you use /EXCLUDE or /INCLUDE, you need to have a consistent set of PAKs registered across all licensing databases present in the OpenVMS Cluster.

If your software license permits it, you can use the following two commands to transfer license PAKs:


To display the particular license(s) required (such as when you receive a NOLICENSE error), use the following DCL sequence:


This logical name will cause all license failures to generate OPCOM messages, and this will hopefully show which license(s) you need--- there may well also be additional license failures displayed, as various products can check for and can be enabled by multiple license PAKs. You will want to deassign this logical name when done.

Some of the more common license PAKs:

  TCP/IP Services:   UCX, or NET-APP-SUP* 
  OpenVMS VAX:       VAX-VMS 
  OpenVMS Galaxy:    OPENVMS-GALAXY 
  Cluster (Alpha):   VMSCLUSTER, NET-APP-SUP* 
  Cluster (VAX):     VAXCLUSTER, NET-APP-SUP* 

Various NET-APP-SUP (NAS) license packages are available, each with differing collections of products authorized. See the various NAS Software Product Description (SPD) documents for specific details.

To determine which license PAK is failing (via a license check failure OPCOM message), use the command:


Realize that defining this logical name will cause license checks that are otherwise hidden (unimplemented, latent, or part of a check for any of a series of licenses) to become visible. In other words, expect to see some spurious license check calls when you define this.

For information on PAKGEN and on generating license PAKs, please see Section 10.10.

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