Technical data

System Management Release Notes

5.18 Volume Shadowing for OpenVMS

$DISMOUNT/POLICY=MINICOPY $80$DKA302:

%DISM-W-CANNOTDMT, $80$DKA302: cannot be dismounted

%DISM-F-SRCMEM, only source member of shadow set cannot be dismounted

$DISMOUNT/POLICY=MINICOPY $80$DKA302:

This problem will be corrected in a future release.

5.18.4 SHADOW_MAX_UNIT Settings

V7.3

OpenVMS Alpha Version 7.3 introduces minicopy support in Volume Shadowing

for OpenVMS.

As part of the minicopy functionality, a new volume shadowing system parameter,

SHADOW_MAX_UNIT, is provided for specifying the maximum number of

shadow sets that can exist on a node. The default value on OpenVMS Alpha

systems is 500; on OpenVMS VAX systems, the default is 100. This system

parameter is not dynamic; a reboot is required to make the change take effect.

Caution

Review carefully the default settings of SHADOW_MAX_UNIT for your

conﬁguration. Dismounted shadow sets, unused shadow sets, and shadow

sets with no write bitmaps allocated to them are included in this total.

The setting must be equal to or greater than the number of shadow sets

you plan to have on a system. Any MOUNT command that attempts to

create more than the maximum speciﬁed by SHADOW_MAX_UNIT fails.

Note that this parameter does not affect the naming of shadow sets. For example,

with the default value of 100, a device name such as DSA999 is still valid.

5.18.5 SHADOW_MAX_COPY VAX Setting for Using Minicopy in

Mixed-Architecture Cluster

V7.3

OpenVMS Version 7.3 supports minicopy on standalone Alpha systems, in an

OpenVMS Cluster system consisting entirely of Alpha systems, and in a mixed-

architecture OpenVMS Cluster system consisting of Alpha and VAX systems. It

is possible, although highly unlikely, in a mixed-architecture cluster that a VAX

system could be assigned the task of adding a member to a shadow set. Because

a VAX system cannot perform a minicopy, it would perform a full copy.

To prevent this from happening, Compaq advises you to set the SHADOW_MAX_

COPY system parameter to 0 on any VAX systems in the cluster if you intend to

use this new minicopy feature.

5.18.6 HSD10 Virtual Disks

V7.1

The HSD10 controller supports a virtual disk capability by partitioning physical

disks. To prevent data corruption, do not use OpenVMS Volume Shadowing to

create shadow sets using HSD10 virtual disks.

System Management Release Notes 5–35