Aborts mount verification on the specified shadow set or on all shadow
sets in mount verification on the system.
Use this qualifier when you know that the unit cannot be recovered.
When you use this qualifier, the shadow set must be in mount
verification. The shadow set aborts mount verification immediately on
the system from which the command is issued. If the shadow set is not
in mount verification, this command returns the error
%SYSTEM-E-UNSUPPORTED, unsupported operation or function.
After this command completes, the shadow set still must be dismounted.
Use the following command to dismount the shadow set:
$ DISMOUNT/ABORT/OVERRIDE=CHECKS DSAn:
Causes the command to operate on all shadow sets that are mounted on
the system from which the command is issued.
/ALL can be used instead of DSAn: in most commands that take a
shadow set device specification as a parameter. Exceptions are
/DEMAND_MERGE, /DELETE, and /EVALUATE=RESOURCES. /ALL also cannot be
specified with /POLICY or any qualifier that operates only on
individual shadow set members (for example, /MEMBER_TIMEOUT and
Specifies whether a query is made before each merge operation to
confirm that the operation should be performed on the designated shadow
This qualifier can be used only in conjunction with the /DEMAND_MERGE
The following responses are valid in response to the query:
- Affirmative: YES, TRUE, or 1
- Negative: NO, FALSE, 0 (zero), or pressing the Return key.
- End the process: QUIT or Ctrl/Z
- When you enter ALL, the command continues to process, but no
further prompts are given.
You can enter word responses in uppercase or lowercase letters, and
words can be abbreviated to one or more letters. If you enter an
illegal response, DCL redisplays the prompt. (See the SET SHADOW
Specifies which source member of a shadow set to use as the source for
read data during full copy operations when a third member is added to a
shadow set that contains two full members. This qualifier affects only
those copy operations that do not use disk copy data (DCD) commands.
The source specified by this qualifier persists until the shadow set is
Some storage controllers, such as the HSG80, have a read-ahead cache,
which significantly improves a device's read performance. Copy
operations normally alternate reads between the two source members,
which effectively nullifies the benefits of the read-ahead cache. This
qualifier lets you force all reads from a single, specified source
member for the duration of a copy operation.
In addition to improving copy performance, /COPY_SOURCE can be used to
prevent read operations from a specific shadow set member that is
considered unreliable. By specifying only the healthy shadow set
member, the copy operations can continue to completion. The unreliable
shadow set member can be removed once the copy operation completes
If a shadow set (DSAn:) is specified, all reads for full copy
operations are performed from the device that is the current
"master" member, regardless of the physical location of that
If a shadow set member (ddcu:) is specified, that member is
used as the read source for all copy operations. This setting allows
you to choose any source member. For example, you can choose a source
member that is at the same site as the member being added, rather than
using a master member that is not at the same site.
If /ALL is specified, all reads for full copy operations on all
currently mounted virtual units are performed from the master member.
Used in conjunction with /POLICY=HBMM, /DELETE removes a host-based
minimerge (HBMM) policy from a specified shadow set, or deletes an HBMM
named policy from the entire cluster. For example, the following
command removes the policy that is currently associated with shadow set
$ SET SHADOW /DELETE DSA1 /POLICY=HBMM
In contrast, the following command removes COMPANY_POLICY from the
$ SET SHADOW /DELETE /NAME=COMPANY_POLICY /POLICY=HBMM
You cannot delete the NODEFAULT policy.
You cannot specify /ALL with /DELETE.
Initiates a merge operation on the specified shadow set. This qualifier
is useful if the shadow set was created with the INITIALIZE/SHADOW
command without the use of the /ERASE qualifier. For more information
about using /DEMAND_MERGE, see the HP Volume Shadowing for OpenVMS manual.
You cannot specify /ALL with /DEMAND_MERGE.
An OPCOM message is displayed for each shadow set indicating that a
demand merge has been invoked and recording the process ID (PID) of the
process that executed the command. For example:
%%%%%%%%%%% OPCOM 9-MAR-2004 10:35:23.24 %%%%%%%%%%%
Message from user SYSTEM on NODE1
Demand Merge requested for _DSA721:, PID: 2760009A
Disables host-based minimerge (HBMM) on the specified shadow set or
clusterwide on all shadow sets.
/DISABLE=SPLIT_READ_LBNS disables the split behavior of logical block
numbers and as a result the reads are alternated between the source
shadow set members having the same read_cost and device queue length.
Enables host-based minimerge (HBMM) on the specified shadow set or
across the entire cluster if an applicable HBMM policy exists.
/ENABLE=SPLIT_READ_LBNS logically divides the shadow set members having
the same read cost into equal groups of Logical Block Numbers (LBNs).
When a virtual unit performs a read, it does so by reading from the
corresponding LBN group. This results in the maximum usage of the
controller read-ahead cache.
Forces the system to evaluate whether it should act on most shadow copy
and merge operations currently being managed on the system. It cancels
most operations and then, based on the value of system parameter
SHADOW_MAX_COPY and the copy/merge priority of each shadow set), it
evaluates the order in which the pending copies and merges should be
RESOURCES is the only supported value for /EVALUATE, and it must be
/EVALUATE does not apply to MSCP-based minimerge operations. MSCP-based
minimerge operations are not subject to cancellation and restart by
This command is intended to be used after changing the value of the
dynamic system parameter SHADOW_MAX_COPY or after issuing a SET SHADOW
/PRIORITY=n command for a shadow set. After a suitable delay,
all available SHADOW_MAX_COPY slots on the system are allocated using
the priority list.
Expels the specified shadow set member from the shadow set. The
specified device must be a member of a shadow set that is mounted on
the system where the command is issued. You cannot specify /ALL with
If connectivity to a device has been lost and the shadow set is in
mount verification, this qualifier causes the member to be expelled
from the shadow set immediately.
If the shadow set is not currently in mount verification, no immediate
action is taken. If connectivity to a device has been lost but the
shadow set is not in mount verification, this qualifier lets you flag
the member to be expelled from the shadow set as soon as the shadow set
enters mount verification. If no action has been taken on the specified
member and you wish to clear the flag, use /NOFORCE_REMOVAL.
If the shadow set is dismounted before the member is expelled, the
FORCE_REMOVAL request expires.
Instructs the volume shadowing software to display a brief message
confirming that the SET SHADOW command completed. If /OUTPUT is also
specified, this information is written to the output file.
Specifies the timeout value to be used for a shadow set member. The
specified device must be a member of a shadow set that is mounted on
the system where the command is issued.
The value supplied by this qualifier overrides the system parameter
SHADOW_MBR_TMO for this specific device. Each member of a shadow set
can be assigned a different MEMBER_TIMEOUT value.
The valid range for n is 1 through 16777215 seconds.
The timeout value set by /MEMBER_TIMEOUT does not persist after the
shadow set is dismounted.
Specifies the mount verification timeout value to be used for all
shadow sets on the cluster or for the shadow set specified by its
virtual unit name (DSAn:). The specified shadow set must be
mounted on the system where the command is issued.
The value supplied by this qualifier overrides the value specified by
the system parameter MVTIMEOUT for this specific shadow set.
You cannot change the value of MVTIMEOUT for a system disk. Any attempt
to do so results in an error.
The valid range for n is 1 through 16777215 seconds.
The timeout value set by /MVTIMEOUT does not persist after the shadow
set is dismounted.
Used with /POLICY=HBMM to define a named host-based minimerge (HBMM)
policy or used with /DELETE to delete a policy. The policy is defined
clusterwide. See detailed descriptions under /DELETE and /POLICY.
Policy names are case insensitive and must consist of from 1 to 64
characters. Only letters, numbers, the dollar sign ($), and the
underscore (_) are allowed.
If you create a default policy, you must assign it the name DEFAULT.
For details about creating and using policy names, see the
HP Volume Shadowing for OpenVMS manual.
Outputs any messages to the specified file.
Creates or deletes a policy for host-based minimerge (HBMM).
HBMM is the only supported value for the /POLICY qualifier, and it must
be included. You can optionally specify a named policy, including
DEFAULT, or you can specify NODEFAULT to indicate that the shadow set
to which it is applied is not to use HBMM, including any DEFAULT
policy. For details about specifying policies and using the DEFAULT and
NODEFAULT policy names, see the HP Volume Shadowing for OpenVMS manual.
When /POLICY is specified with /DELETE, it removes either a specified
HBMM named policy or the HBMM policy for a specific shadow set. You
cannot delete the NODEFAULT policy.
When /POLICY is specified with /NAME, it defines a clusterwide named
policy. When no qualifiers other than /NAME or /DELETE are specified,
/POLICY defines a policy for a specific shadow set.
Deleting bitmaps with the DELETE/BITMAP command causes a bitmap to be
deleted. However, the shadowing software recognizes this condition and
starts a new bitmap immediately. To disable HBMM bitmaps, you have to
use the command SET SHADOW/DISABLE=HBMM.
When defining a policy, you use five keywords (MASTER_LIST, COUNT,
RESET_THRESHOLD, MULTIUSE, and DISMOUNT) to control the placement and
management of HBMM bitmaps. An HBMM policy specification consists of a
list of these keywords enclosed within parentheses. Only the
MASTER_LIST keyword is required. If COUNT and RESET_THRESHOLD are
omitted, default values are applied.
The MULTIUSE and DISMOUNT keywords specify the number of bitmaps to be
converted to multiuse bitmaps during the automatic and manual removal
of members respectively. If MULTIUSE is omitted, then automatic
minicopy on volume processing is not enabled. As a result, no HBMM
bitmap is converted to multiuse bitmap. If DISMOUNT is omitted, only a
maximum of 6 HBMM bitmaps can be used as multiuse bitmaps.
The MASTER_LIST keyword is
used to identify a set of systems as candidates for a master bitmap.
The list value can be a single system name; a parenthesized,
comma-separated list of system names; or the wildcard character, as
shown in the following examples:
When the system list consists of a single system name or the
wildcard character, parentheses are optional.
An HBMM policy must
include at least one MASTER_LIST. Multiple master lists are optional.
If a policy has multiple master lists, the entire policy must be
enclosed with parentheses, and each constituent master list must be
separated by a comma as shown in the following example:
There is no significance to the position of a system name in a
The COUNT keyword specifies how many
systems in the master list can have master bitmaps. Therefore, the
COUNT keyword and its associated MASTER_LIST must be enclosed within a
single parenthetical statement.
The COUNT value specifies the
number of systems on which you want master bitmaps. It does not
necessarily mean that the first n systems in the list will be
When the COUNT keyword is omitted, the default value is 6
or the number of systems in the master list, whichever is smaller.
You cannot specify more than one COUNT keyword per master list.
The RESET_THRESHOLD keyword
specifies the number of blocks that can be set before the bitmap is
eligible to be cleared. Each set bit in a master bitmap corresponds to
a set of blocks to be merged, so this value can affect the merge time.
Bitmaps are eligible to be cleared when the RESET_THRESHOLD is
exceeded. However, the reset is not guaranteed to occur immediately
when the threshold is crossed. For more information about choosing a
value for this attribute, see the HP Volume Shadowing for OpenVMS manual.
threshold is associated with a specific HBMM policy, so the
RESET_THRESHOLD keyword can be defined only once in a policy
specification. Because its scope is the entire policy, the
RESET_THRESHOLD keyword cannot be specified inside a constituent master
list when the policy uses multiple master lists.
RESET_THRESHOLD keyword is omitted, the value of 1,000,000 is used by
default. See the following example:
(MASTER_LIST=*, COUNT=4, RESET_THRESHOLD=1000000)
The command in the following example
defines the HBMM named policy POLICY_2, which has two master lists.
Having multiple master lists can be useful in a multiple-site OpenVMS
Cluster configuration because a policy can be defined to ensure that at
least one surviving system has an HBMM bitmap in the event of an outage
at one or more sites.
$ SET SHADOW /POLICY=HBMM=( -
_$ (MASTER_LIST=(NODE1,NODE2,NODE3), COUNT=2), -
_$ (MASTER_LIST=(NODE4,NODE5,NODE6), COUNT=2), -
_$ RESET_THRESHOLD=150000) -
In a policy with multiple master lists, a given system name can
appear in only one master list.
A shadow set need not be mounted to
have an HBMM policy defined for it.
See the SET SHADOW Examples
section for several more /POLICY examples.
The MULTIUSE keyword enables
automatic minicopy on volume processing. n specifies the
number of existing HBMM master bitmaps to be converted to multiuse
bitmaps in the event that a shadow set member is removed from the
shadow set by the shadowing driver.
During a loss of connectivity
to a site or controller, shadowing may remove a member from the shadow
set. When the member is added back to the shadow set, a full shadow
By converting a few of the HBMM bitmaps to multiuse,
all writes that are performed to the shadow set are recorded. Thus,
when the member is added back to the shadow set, the multiuse bitmap
can be used for a minicopy operation. This is much faster than a full
The value of n cannot exceed the implied
or explicit value of COUNT. If MULTIUSE is not specified, then bitmaps
are not converted to multiuse and a full copy operation is required.
Fatal drive errors that remove a shadow set member do not cause a
multiuse conversion as the drive has to be replaced and therefore
requires a full copy operation.
The DISMOUNT keyword allows all the
12 write bitmaps to be used by Shadowing as multiuse bitmaps, thereby
reducing the single point of failure of single minicopy master bitmaps.
n specifies the number of HBMM bitmaps to be converted to
multiuse bitmaps every time a member is dismounted from a shadow set
with the following command:
Overrides the current default priority setting. Priorities range from 0
(lowest) to 10000 (highest). The default priority is 5000. A shadow set
with a priority of 0 is never considered for a merge or a copy on the
When a recovery operation (that is, either a merge or a copy) is needed
on multiple shadow sets, the shadow sets are recovered in priority
order from highest to lowest. The priority setting is system specific;
any change in priority made on a single system does not propagate to
the entire cluster and does not persist across a system reboot.
Once this qualifier has been applied to a virtual unit that is mounted,
the setting persists across any subsequent DISMOUNT and MOUNT commands.
Enables you to modify the default cost assigned to each shadow set
member (ddcu:). By modifying the assignments, you can bias the
reads in favor of one member of a two-member shadow set or, in the case
of three-member shadow sets, in favor of one or two members of the set
over the remaining members. The device specified must be a shadow set
or member of a shadow set that is mounted on the system where the
command is issued.
The valid range for the specified cost is 1 through 65,535 units.
The shadowing driver assigns default READ_COST values to shadow set
members when each member is initially mounted. The default value
depends on the device type and its configuration relative to the system
mounting it. The following list of device types is ordered by the
default READ_COST assignments, from the lowest cost to the highest cost:
- DECram device
- Directly connected device in the same physical location
- Directly connected device in a remote location
- DECram served device
- Default value for other served devices
The value supplied by the /READ_COST qualifier overrides the default
assignment. The shadowing driver adds the value of the current queue
depth of the shadow set member to the READ_COST value and then reads
from the member with the lowest value.
Different systems in the cluster can assign different costs to each
shadow set member.
When this qualifier specifies a shadow set (DSAn:) instead of
a shadow set member, the /READ_COST qualifier switches the read cost
setting for all shadow set members back to the default read
cost settings established automatically by the shadowing software. The
specified shadow set must be mounted on the system where the command is
You cannot specify a value for /READ_COST when you specify /ALL.
If the /SITE command qualifier has been specified, the shadowing driver
takes site values into account when it assigns default READ_COST
values. In order for the shadowing software to determine whether a
device is in the category of "directly connected device in a
remote location," the /SITE command qualifier must have been
applied to both the shadow set and the shadow set member.
Reads requested for a shadow set from a system at site 1 are performed
from a shadow set member that is also at site 1. Reads requested for
the same shadow set from site 2 can read from the member located at
Allows the system manager to adjust the rating assigned to a system
based on a delay assessed for each MSCP served shadow set member on
that system. The value specified by this qualifier overrides the value
established by the SHADOW_PSM_RDLY system parameter. The default delay
for each MSCP served member is 30 seconds and the valid range for the
specified delay is 0 through 65,535 seconds.
When a copy or merge operation is needed on a shadow set that is
mounted on multiple systems, OpenVMS Volume Shadowing attempts to
perform this work on a system that has a local connection to all of the
shadow set members. Systems are rated with a penalty (delay time)
assessed for each shadow set member that is MSCP served to the system.
No delay is added for local members, so a system with all locally
accessible shadow set members is likely to perform the work before a
system where one or more members is served.
IF /ALL is also specified, the specified delay is applied to all
currently mounted shadow sets.
See the HP Volume Shadowing for OpenVMS manual for more information.
Resets the shadowing specific counters that are maintained for each
shadow set. These counters can be displayed using the SHOW SHADOW
The counters that are reset to 0 are the following:
HBMM Reset Count
SCP Merge Repair Cnt
APP Merge Repair Cnt
The HBMM Reset Count is a running total of the number of times that the
HBMM Reset Threshold was exceeded and therefore, the number of times
the bitmaps were reset. (The threshold is set by the RESET_THRESHOLD
keyword in the /POLICY qualifier.) For more information, see the
HP Volume Shadowing for OpenVMS.
Indicates to the shadowing driver the site location of the specified
shadow set (DSAn:) or shadow set member (ddcu:).
The SHADOW_SITE_ID system parameter defines the default site location
of the shadow set. You can override the default location of the shadow
set with the /SITE qualifier.
The valid range for the site location, represented by n, is 1
If /ALL is specified, all virtual units are assigned the new value. The
shadow set's member site values remain unchanged.
After you apply this qualifier, the setting remains in effect until you
change it using a SET SHADOW/SITE command.
This qualifier can improve read performance because the member that is
physically local to the system will be the preferred disk from which to
read, provided that you specify the /SITE qualifier for each shadow set
member and for the shadow set. (In a Fibre Channel configuration,
shadow set members at different sites are directly attached to the
system. For the Volume Shadowing and OpenVMS Cluster software, there is
no distinction between local and remote in multiple-site Fibre Channel
Using /STALL=WRITES[=nnn] qualifier, you can stall the write operations
for nnn seconds. nnn is the number of seconds for
which you can stop write operations. If no value is specified for
nnn, the lock is released after SHADOW_MBR_TMO seconds. The
default is SHADOW_MBR_TMO.
/NOSTALL=WRITES[=nnn] releases the lock after nnn seconds so
that write operations can continue on the shadow set.