HP OpenVMS Systems Documentation

HP OpenVMS Version 8.2 Release Notes

This chapter contains information that you need to know before installing OpenVMS I64 Version 8.2 or installing or upgrading to OpenVMS Alpha Version 8.2. Topics of interest to both Alpha and I64 users are covered first. Later sections group notes of interest to users of specific platforms.

HP recommends that you read all of the following manuals before installing or upgrading OpenVMS Version 8.2:

• HP OpenVMS Version 8.2 Release Notes (this manual)
• HP OpenVMS Version 8.2 New Features and Documentation Overview
• HP OpenVMS Version 8.2 Upgrade and Installation Manual

Refer to Chapter 6 for hardware release notes and to Chapter 2 for information about associated products.

1.1 HP Software Technical Support Policy

HP provides software technical support for OpenVMS operating system software for the latest, currently shipping version and the immediate prior version of the product. Each version is supported for 24 months from its release date, or until the release of the second subsequent version, whichever is greater. "Version" is defined as a release containing new features and enhancements. Patch kits and maintenance-only releases do not meet the definition of "version" in the context of this support policy.

Current version-level support (Standard Support or SS) and Prior Version Support (PVS) for OpenVMS operating system software is provided for OpenVMS versions in accordance with these guidelines. The current level of support for recent versions of OpenVMS Alpha and OpenVMS VAX is kept up to date on this web page:

The Operating System Support Policy applies to all OpenVMS Major Releases, New Feature Releases, and Enhancement releases, which are defined as follows:

• Major Releases for OpenVMS contain substantial new functionality. The version number increases to the next integer (for example, from 6.2-1H1 to 7.0).
  Application impact: OpenVMS internal interfaces have changed. Although binary compatibility will be maintained for the majority of applications, independent software vendors (ISVs) should test on the new version and may need to release a new application kit. Some application partners may want to release a new application kit to take advantage of new features in the operating system.
• New Feature Releases for OpenVMS contain new features, enhancements, and maintenance updates. The version number increases to the next decimal number (for example, from 7.2 to 7.3).
  Application impact: The release has not retired any published application programming interfaces (APIs). However, OpenVMS internal interfaces may have been modified with the addition of significant new functionality or implementation of performance improvements. It is unlikely that a new application kit will be required for 95 percent of all applications that use documented APIs. Device driver and kernel-level applications (that is, those that use nonstandard or undocumented APIs) may need qualification testing.
• Enhancement Releases for OpenVMS contain enhancements to existing features and maintenance updates. The version number increases to show a revision by using a dash (for example, OpenVMS Version 7.3-2).
  Application impact: The release may contain new hardware support, software enhancements, and maintenance, but the changes are isolated and have no impact on applications that use published APIs. There is no need for ISVs to test on the new release or to produce a new application kit.
• Hardware Releases provide current version-level support until 12 months after a subsequent release containing that particular hardware support. Hardware releases are shipped with new hardware sales only and are not distributed to existing service customers.

The following OpenVMS core products are supported at the same level (Standard Support or Prior Version Support) and duration as the operating system version on which they ship:

• HP Advanced Server for OpenVMS
• HP DECnet (Phase IV)
• HP DECnet-Plus for OpenVMS
• HP OpenVMS Cluster Client Software
• HP OpenVMS Cluster Software for OpenVMS
• HP PathWorks or HP PATHWORKS for OpenVMS
• HP RMS Journaling for OpenVMS
• HP TCP/IP Services for OpenVMS
• HP Volume Shadowing for OpenVMS

These products require their own individual support contracts and are not included in the operating system support contract.

1.2 General Application Compatibility Statement

OpenVMS has consistently held the policy that published APIs are supported on all subsequent releases. It is unlikely applications that use published APIs will require changes to support a new release of OpenVMS. APIs may be "retired," and thus removed from the documentation; however, the API will continue to be available on OpenVMS as an undocumented interface.

1.3 Obtaining Remedial Kits

Remedial kits for HP products are available online at the HP IT Resource Center (ITRC). Use of the ITRC patch download site requires user registration and login. Registration is open to all users and no service contract is required. You can register and log in from the following URL:

You can also use FTP to access patches from the following location:

V8.2

OpenVMS provides customers with the flexibility to choose the network protocol of their choice. Whether you require DECnet or TCP/IP, OpenVMS allows you to choose the protocol or combination of protocols that works best for your network. OpenVMS can operate with both HP and third-party networking products.

During the main installation procedure for OpenVMS Version 8.2, you have the option of installing the following supported HP networking software:

• Either HP DECnet-Plus Version 8.2 for OpenVMS or HP DECnet Phase IV Version 8.2 for OpenVMS. (Note that both DECnet products cannot run concurrently on your system.)
  DECnet-Plus contains all the functionality of the DECnet Phase IV product, plus the ability to run DECnet over TCP/IP or OSI protocols.
  Support for DECnet Phase IV is provided to customers with a Prior Version Support Contract. For more information about the Prior Version Support service, see Section 1.1.
• HP TCP/IP Services for OpenVMS Version 5.5
  TCP/IP Services and DECnet can run concurrently on your system. Once you have installed HP DECnet-Plus for OpenVMS and TCP/IP Services on your system, you can run DECnet applications and OSI applications, or both, over your TCP/IP network. Refer to the DECnet-Plus for OpenVMS Management Guide for more information about running DECnet over TCP/IP (RFC 1859) and OSI over TCP/IP (RFC 1006).

Alternatively, after you install OpenVMS, you can install your choice of another third-party networking product that runs on OpenVMS Version 8.2.

For information about how to configure and manage your HP networking software after installation, refer to the TCP/IP, DECnet-Plus, or DECnet documentation. The manuals are available in online format on the OpenVMS Documentation CD-ROM; printed manuals can be ordered from HP (800-282-6672).

1.5 Disk Incompatibility with Older Versions of OpenVMS

V8.2

The OpenVMS Version 8.2 installation procedure initializes the target disk with volume expansion (INITIALIZE/LIMIT). This renders the disk incompatible with versions of OpenVMS prior to Version 7.2. In most cases, this does not present a problem. However, if you intend to mount this new disk on a version of OpenVMS prior to Version 7.2, you must first take steps to make the disk compatible for that operating system version. Refer to the HP OpenVMS Version 8.2 Upgrade and Installation Manual for detailed instructions.

Note that by taking these steps, your new system disk might include a relatively large minimum allocation size (as defined by /CLUSTER_SIZE). As a result, small files will use more space than necessary. Therefore, you should perform these steps only for system disks that must be mounted on versions of OpenVMS prior to Version 7.2.

V8.2

The following table lists which versions of DECwindows Motif are supported on various platforms of the OpenVMS Version 8.2 operating system.

The DECwindows Motif software relies on specific versions of OpenVMS server and device driver images. Be sure to install or upgrade to the version of DECwindows Motif that is appropriate to your operating system environment, as noted in Table 1-1.

For information on support for prior versions of DECwindows Motif, see the HP DECwindows Motif for OpenVMS Release Notes.

For detailed information about installing the DECwindows Motif software, refer to the HP DECwindows Motif for OpenVMS Installation Guide.

1.7 HP SSL: Installing HP SSL V1.2

V8.2

Installing HP SSL V1.2 on your Alpha or I64 system provides you with new ciphers and algorithms as well as the latest security fixes from openssl.org. The HP SSL V1.2 kit is included with the layered products distribution. HP recommends that you install HP SSL V1.2 after you install or upgrade your operating system and TCP/IP Services for OpenVMS.

You must manually remove any previous versions of SSL before installing SSL V1.2. Use the following commands to remove and install SSL:

$ PRODUCT REMOVE SSL
$ PRODUCT INSTALL SSL /SOURCE=ddcu:[directory]

For details about installing and using SSL, refer to the HP Open Source Security for OpenVMS, Volume 2: HP SSL for OpenVMS manual.

1.8 Release Notes for OpenVMS I64 Users

The following notes are primarily of interest to users of OpenVMS I64 systems.

1.8.1 HP Integrity Server Configurations

V8.2

The OpenVMS I64 Version 8.2 release supports all of the standard system features and core I/O on the rx1600-2, rx1620-2, rx2600-2, rx2620-2, and rx4640-8 Integrity servers.

For OpenVMS I64 Version 8.2, there are two primary storage interconnects:

• The SCSI storage type is U320, used for core I/O for certain Integrity server systems, as well as the A7173A U320 SCSI adapter. For connection to external SCSI storage, the supported storage shelves are the DS2100 or the MSA30.
• The external Fibre Channel storage connection is through the dual-port 2GB Fibre Channel Universal PCI-X adapter (A6826A). This adapter allows for connectivity to any external SAN-based Fibre Channel storage infrastructure supported by OpenVMS.

Customers who used any earlier evaluation or field test kits should note the following important considerations:

• In the SCSI adapter area, the U160 adapter (A6829A) is not officially supported on OpenVMS I64 Version 8.2, and will reach end-of-life during 2005. However, you can use this adapter for existing hardware configurations as long as the system remains as it is currently configured. Any additional adapters, or movement to another server, require the U320 SCSI adapter technology.
• In the case of Fibre Channel, customers might have been running with the AB232A or KGPSA-EA FC adapters. These adapters are not supported on OpenVMS I64 Version 8.2, and customers using them must upgrade to the A6826A FC adapter before running production applications on Version 8.2.

V8.2

HP Integrity servers maintain a System Event Log (SEL) within system console storage, and OpenVMS I64 automatically transfers the contents of the SEL into the OpenVMS error log. If you are operating from the console during a successful boot operation, you might see a message indicating that the Baseboard Management Controller (BMC) SEL is full. You can safely continue when the BMC SEL is full by following the prompts; OpenVMS will process the contents of the SEL. If you wish to clear the SEL manually, enter the following command at the EFI Shell prompt:

Shell> clearlogs SEL

This command deletes the contents of the SEL. The command is available with current system firmware versions.

If your Integrity server is configured with a Management Processor (MP) and you see a BMC event log warning while connected to the MP console, you can clear the BMC event log by using MP. Press Ctrl/B to drop to the MP> prompt. At the MP> prompt, enter SL (from the main menu) and use the C option to clear the log.

HP recommends that you load and use the most current system firmware. For more information about updating the system firmware, refer to the HP OpenVMS Version 8.2 Upgrade and Installation Manual.

1.8.3 Firmware for Integrity Servers

V8.2

OpenVMS I64 Version 8.2 was tested with the latest firmware for each of the supported Integrity servers. The following table lists the recommended firmware versions:

Some new rx4640 servers require, and will ship with, the higher firmware versions shown in the table. As this manual goes to press, the lower firmware versions are the latest released to customers to update existing servers. OpenVMS has been tested with both versions of firmware. HP recommends that all rx4640 servers be updated to the higher firmware versions when the firmware is released.

To check the firmware versions for your server, use the Extensible Firmware Interface (EFI) command INFO FW, as shown in the following example. (For instructions on how to access and use EFI, refer to the HP OpenVMS Version 8.2 Upgrade and Installation Manual.)

Shell> INFO FW

FIRMWARE INFORMATION

   Firmware Revision: 2.13 [4412]          (1)

   PAL_A Revision: 7.31/5.37
   PAL_B Revision: 5.65
   HI Revision: 1.02

   SAL Spec Revision: 3.01
   SAL_A Revision: 2.00
   SAL_B Revision: 2.13

   EFI Spec Revision: 1.10
   EFI Intel Drop Revision: 14.61
   EFI Build Revision: 2.10

   POSSE Revision: 0.10

   ACPI Revision: 7.00

   BMC Revision: 2.35                       (2)
   IPMI Revision: 1.00
   SMBIOS Revision: 2.3.2a
   Management Processor Revision: E.02.29   (3)

1. The system firmware revision is 2.13.
2. The BMC firmware revision is 2.35.
3. The MP firmware revision is E.02.29.

The HP Integrity rx4640 server contains Dual Hot Plug Controller (DHPC) hardware with upgradable firmware. To check the current version of your DHPC firmware, use the EFI command INFO CHIPREV, as shown in the following example. The hot-plug controller version will be displayed. A display of 0100 indicates version 1.0; a display of 0110 means version 1.1.

Shell> INFO CHIPREV

CHIP REVISION INFORMATION

   Chip                  Logical     Device       Chip
   Type                     ID         ID       Revision
   -------------------   -------     ------     --------
   Memory Controller         0       122b         0023
   Root Bridge               0       1229         0023
     Host Bridge          0000       122e         0032
     Host Bridge          0001       122e         0032
     Host Bridge          0002       122e         0032
     Host Bridge          0004       122e         0032
      HotPlug Controller     0          0         0110
     Host Bridge          0005       122e         0032
      HotPlug Controller     0          0         0110
     Host Bridge          0006       122e         0032
     Other Bridge            0          0         0002
       Other Bridge          0          0         0008
         Baseboard MC        0          0         0235

For instructions on upgrading your firmware, refer to the HP OpenVMS Version 8.2 Upgrade and Installation Manual.

1.8.4 Booting On a Fibre Channel Storage Device

V8.2

Many customers prefer to boot from a Fibre Channel (FC) storage device because of its speed and because it can serve as a common cluster system disk in a SAN. Booting on a FC storage device on OpenVMS I64 systems is significantly different from booting on a FC storage device on OpenVMS Alpha systems.

Refer to the Fibre Channel chapter of Guidelines for OpenVMS Cluster Configurations for directions on how to configure and boot from a FC device on OpenVMS I64 systems.

1.8.5 Booting from the Installation DVD

V8.2

On I64 systems with the minimum amount of supported memory (512MB), the following message appears when booting from the installation DVD:

********* XFC-W-MemmgtInit Misconfigure Detected ********
XFC-E-MemMisconfigure MPW_HILIM + FREEGOAL > Physical Memory and no reserved memory for XFC
XFC-I-RECONFIG Setting MPW$GL_HILIM to no more than 25% of physical memory XFC-I-RECONFIG
Setting FREEGOAL to no more than 10% of physical memory
********* XFC-W-MemMisconfigure AUTOGEN should be run to correct configuration ********
********* XFC-I-MemmgtInit Bootstrap continuing ********

The message means that the system cache (XFC) initialization has successfully adjusted the SYSGEN parameters MPW_HILIM and FREEGOAL to allow caching to be effective during the installation. You can continue with the installation.

1.8.6 Setting Up I64 Systems to Reboot

V8.2

An I64 system does not automatically reboot unless it has been set up to do so from the console. In a cluster, the Alpha systems will reboot, but the I64 systems will shut down and sit at the console prompt.

For details about how to set up your I64 system to reboot, refer to the HP OpenVMS Version 8.2 Upgrade and Installation Manual.

1.8.7 HP DECwindows Motif Release Notes

The following DECwindows Motif release notes are of interest to OpenVMS I64 users.

1.8.7.1 Keyboard Support

V8.2

The only model keyboard supported on HP DECwindows Motif for OpenVMS I64 systems is the LK463 keyboard. Although other types of keyboards may function in the OpenVMS I64 environment, HP does not currently support them.

1.8.7.2 Connect Peripheral Devices Prior to Server Startup

V8.2

To properly configure your system as a DECwindows X display server, you must have all the following peripheral components connected prior to startup:

• monitor
• USB mouse
• USB keyboard

Otherwise, the server system might not complete the device initialization process correctly. For example, starting up a server system without input devices (mouse and keyboard) could result in a blank screen.

To correct this problem, disconnect and reconnect all peripherals.

1.8.7.3 Countdown Messages Displayed During Startup

V8.2

When running DECwindows Motif in client-only mode (with no server configured), messages similar to the following might be displayed during startup:

Waiting for mouse...
Waiting for keyboard...

These messages indicate that device polling is underway and are informational only. They will disappear once the 15-second countdown is complete.

To prevent the messages from displaying, connect the input devices (USB mouse and USB keyboard) to the system prior to startup.

1.9 Release Notes for OpenVMS Alpha Users

The following notes are primarily of interest to users of OpenVMS Alpha systems.

1.9.1 Firmware for OpenVMS Alpha Version 8.2

V8.2

OpenVMS Alpha Version 8.2 was tested with the platform-specific firmware included on Alpha Systems Firmware CD-ROM Version 6.8. For older platforms no longer included on the Firmware CD-ROM, OpenVMS Alpha Version 8.2 was tested with the latest released firmware version. HP recommends upgrading to the latest firmware before upgrading OpenVMS.

The OpenVMS Alpha Version 8.2 kit includes the Alpha Systems Firmware CD-ROM and Release Notes. Read the Release Notes before installing the firmware.

You can obtain Version 6.8 and the latest firmware information from the following website (URL is case sensitive):

V8.2

You can upgrade directly to OpenVMS Alpha Version 8.2 from only the following versions of OpenVMS Alpha. Upgrades to OpenVMS I64 Version 8.2 are not supported.

Version 7.3-2
Version 7.3-1

If you are currently running OpenVMS Alpha Version 6.2x through 7.3, inclusive, you must first upgrade to Version 7.3-1 or 7.3-2, and then to Version 8.2. Note that standard support for OpenVMS Alpha Version 7.3-1 systems ends on March 31, 2005. After that, OpenVMS Alpha V7.3-1 systems will not be under Prior Version Support (PVS). For details about OpenVMS operating system support, see the chart on the following website:

If you are running other versions of OpenVMS that are no longer supported, you must do multiple upgrades in accordance with upgrade paths that were documented for earlier versions.

Cluster Concurrent Upgrades

During a concurrent upgrade, you must shut down the entire cluster and upgrade each system disk. No one can use the cluster until you upgrade and reboot each computer. Once you reboot, each computer will be running the upgraded version of the operating system.

Cluster Rolling Upgrades

During a cluster rolling upgrade, you upgrade each system disk individually, allowing old and new versions of the operating system to run together in the same cluster (a mixed-version cluster). There must be more than one system disk. The systems that are not being upgraded remain available.

Only the following OpenVMS Alpha and OpenVMS VAX versions are supported in mixed-version clusters that include OpenVMS Alpha Version 8.2:

Version 7.3-2 (Alpha)
Version 7.3 (VAX)

If you are upgrading in a cluster environment, rolling upgrades are supported from Version 7.3-2 and 7.3-1 of the OpenVMS Alpha operating system. If you have other versions in a cluster, you cannot do a rolling upgrade until those versions are upgraded to a supported version.

Mixed-version support for all of these versions requires the installation of one or more remedial kits. For more information, see Section 4.18.4.

For a discussion of warranted pairs and migration pairs of OpenVMS operating systems, for complete instructions for installing or upgrading to OpenVMS Alpha Version 8.2, and for instructions on installing OpenVMS I64 Version 8.2, refer to the HP OpenVMS Version 8.2 Upgrade and Installation Manual.

1.9.3 Error on Upgrade from Version 7.3-1

V8.2

When you upgrade an OpenVMS Alpha Version 7.3-1 system disk to Alpha Version 8.2, the following error message might appear during the execution phase:

%PCSI-E-PARUDF, file [SYSLIB]SYS$STARLET_C.TLB was not previously installed
or is present but out of scope; module update skipped
Terminating is strongly recommended.  Do you want to terminate? [YES]

This error message is not appropriate for the circumstances. It incorrectly states that the SYS$STARLET_C.TLB library cannot be updated. The cause of this problem is that a patch kit applied to the Alpha Version 7.3-1 system disk improperly updated a module in the library.

Disregard the recommendation to terminate the upgrade. Answer NO to the prompt Do you want to terminate? [YES] . The upgrade will continue successfully.

1.9.4 Encryption for OpenVMS Alpha: Remove Before Upgrading

V8.2

The Encryption producer name has changed from CPQ to HP for OpenVMS Alpha and Itanium systems. This name is visible in the PCSI filename and the PCSI database. For example, the following pairs demonstrate the old and new names:

CPQ-AXPVMS-ENCRYPT-V0106--1.PCSI
HP-AXPVMS-ENCRYPT-V0106--1.PCSI

CPQ AXPVMS ENCRYPT V1.6
HP AXPVMS ENCRYPT V1.6

For Alpha systems, if the ENCRYPT product was installed from an older kit (that is, a kit where HP is not listed as the Encryption producer), you must first remove ENCRYPT before you upgrade. Use the following commands:

$ PRODUCT REMOVE ENCRYPT
$ PRODUCT INSTALL ENCRYPT

A license is no longer required to use the the HP Encryption product.

1.9.5 HP DECram V3.n: Remove Before Upgrading

V8.2

Starting with OpenVMS Alpha and OpenVMS I64 Version 8.2, DECram ships with the OpenVMS operating system as a System Integrated Product (SIP). Before you upgrade to Version 8.2 on an OpenVMS Alpha system, you must remove any old versions of DECram. Refer to the HP OpenVMS Version 8.2 Upgrade and Installation Manual for details.

More DECram release notes are included in Section 2.13.

1.9.6 Kerberos V1.0: Remove Before Upgrading

V7.3-2

If you installed Kerberos Version 1.0 for OpenVMS using a POLYCENTER Software Installation kit, you must use the POLYCENTER Software Installation utility to remove Kerberos Version 1.0 before you upgrade the operating system. (You do not need to remove Kerberos if you are running Version 2.0 or if Version 1.0 was installed as part of the OpenVMS Version 7.3-1 operating system.)

To remove Kerberos, choose Option 6 "Remove installed products" from the installation CD main menu. During the removal, you are asked whether you want to remove the data and directories. (Data refers to the configuration data files along with the principal database, if one was created.) If you want to save this information for use later, respond "No" to the question. Return to the main menu and perform the upgrade of OpenVMS.

After the upgrade, the new Kerberos directories are located in KRB$ROOT:[*...]. (KRB$ROOT is defined as a system-wide logical name when Kerberos is started.) Kerberos data is either created during configuration or moved from the old Kerberos directories and renamed. If you removed a previously installed Kerberos kit and saved the data and directories, the data will automatically be moved into the new directories and be renamed the first time the Kerberos startup procedure is run after the upgrade.

Start the Kerberos servers by entering the following command:

$ @sys$startup:krb$startup.com

Note that the Kerberos startup procedure moves and renames only known Kerberos files. Users who have created files in the old Kerberos directories must manually move those files.

For more information about installing and configuring Kerberos, refer to HP Open Source Security for OpenVMS, Volume 3: Kerberos.

1.9.7 Converting the LANCP Device Database After Upgrading

V8.2

When you upgrade to OpenVMS Alpha Version 8.2, you might also need to convert the LAN device database to the Version 8.2 format if this is not automatically done by LANACP when LANACP is first run after the upgrade.

To convert the database, issue the following LANCP commands to convert the device database and then to stop LANACP so it can be restarted to use the new database:

$ LANCP
LANCP> CONVERT DEVICE_DATABASE
LANCP> SET ACP/STOP
LANCP> EXIT
$ @SYS$STARTUP:LAN$STARTUP

V7.3-2

When you install or upgrade to OpenVMS Alpha Version 7.3-2 or later, you must also install a new version of DECnet-Plus. One of the reasons that makes this necessary is a change of behavior in AUTOGEN (see Section 4.3).

Unlike the behavior of previous versions, DECnet-Plus for OpenVMS Version 7.3-2 and later now provides product information in NEWPARAMS.DAT records, as required by AUTOGEN. AUTOGEN anticipates this change in DECnet-Plus, so AUTOGEN does not print any warnings when it removes "bad" records from CLU$PARAMS.DAT; AUTOGEN presumes these records were made by an older DECnet-Plus kit and will be replaced by the new DECnet-Plus kit. So, under normal conditions, you will not see any striking differences in behavior during an OpenVMS Version 7.3-2 or later installation or upgrade.

However, if other products do not provide product information in NEWPARAMS.DAT records, as now required by AUTOGEN, AUTOGEN prints warning messages to both the report and the user's SYS$OUTPUT device. The warnings state that AUTOGEN cannot accept the parameter assignment found in NEWPARAMS.DAT (because no product name is attached) and that no records will be added to CLU$PARAMS.DAT. Since no records are added, the expected additions or other alterations to SYSGEN parameters will not be made, which could lead to resource exhaustion. Developers and testers of software products should be aware of this requirement; it may also be of interest to system managers.

This new behavior is intended to protect both the users and providers of layered products. By keeping this information ordered properly so that it can be updated properly, problems resulting from bad updates should be minimized.

A description of NEWPARAMS.DAT and CLU$PARAMS.DAT is included in the AUTOGEN chapter of the HP OpenVMS System Management Utilities Reference Manual.

1.9.9 SHADOW_MAX_UNIT Default Setting and Memory Usage

V7.3-2

This note updates an earlier note that discussed the default settings for this system parameter but did not describe the amount of main memory consumed by the default settings.

OpenVMS Alpha Version 7.3 introduced minicopy support in HP Volume Shadowing for OpenVMS. As part of the minicopy functionality, a new volume shadowing system parameter, SHADOW_MAX_UNIT, was introduced. On OpenVMS Alpha systems, the default value for this system parameter is 500, which consumes 24 KB of main memory. On OpenVMS VAX systems, the default value is 100, which consumes 5 KB of main memory.

If you do not plan to use Volume Shadowing for OpenVMS, you can change the setting to its minimum of 10 (which consumes 480 bytes of main memory). By setting the default to its minimum, you free up 23.5 KB of main memory on an OpenVMS Alpha system and 4.5 KB of main memory on a VAX system.

Recommendations for SHADOW_MAX_UNIT settings for volume shadowing are discussed in the HP Volume Shadowing for OpenVMS manual.