Valid for Alpha and Integrity server systems only.
Changes the characteristics of shadow sets created using
Volume Shadowing for OpenVMS. For more information about volume
shadowing, see the VSI Volume Shadowing for OpenVMS manual.
Requires SYSPRV privilege.
NOTE
The following qualifiers are used exclusively to manage
host-based minimerge (HBMM) operations and do not apply to
other operations:
/DELETE
/DISABLE
/ENABLE
/NAME
/POLICY
If you specify any other (non-HBMM) qualifiers in a command
that includes HBMM qualifiers, the command will fail.
For more information about HBMM, see the VSI Volume Shadowing
for OpenVMS manual.
Format
SET SHADOW [device-name[:]]
1 – Parameter
device-name[:]
Specifies the name of a shadow set (DSAn:) or shadow set member
(ddcu:), depending on the command qualifiers (see parameter
formats specified in some qualifier descriptions).
For most qualifiers that take a shadow set (DSAn:) as a parameter
the /ALL qualifier can be used in place of the shadow set name to
indicate that the requested action applies to all shadow sets on
the system. (Exceptions are noted in the description of /ALL.)
2 – Description
The SET SHADOW command and its qualifiers are designed to give
the user greater control over the behavior of shadow sets. These
commands act upon the shadow set (also known as the virtual unit)
or, in some cases, on the individual shadow set member that you
specify.
Unless otherwise noted, the qualifier settings typically remain
in effect until they are changed using either the SET SHADOW
or SET DEVICE command or until the shadow set or shadow set
member is dismounted. If the shadow set is remounted or a shadow
set member is returned to the shadow set from which it was
dismounted, the settings must be specified again.
Some SET SHADOW qualifiers also can be specified using the SET
DEVICE command, where they have the same effect. However, if
your focus is on changing characteristics of shadow sets, the SET
SHADOW command provides more options.
3 – Qualifiers
3.1 /ABORT_VIRTUAL_UNIT
/ABORT_VIRTUAL_UNIT DSAn:
/ABORT_VIRTUAL_UNIT /ALL
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
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:
3.2 /ALL
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
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
/FORCE_REMOVAL).
3.3 /CONFIRM
/CONFIRM
/NOCONFIRM (default)
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
Specifies whether a query is made before each merge operation to
confirm that the operation should be performed on the designated
shadow set.
This qualifier can be used only in conjunction with the /DEMAND_
MERGE qualifier.
The following responses are valid in response to the query:
o Affirmative: YES, TRUE, or 1
o Negative: NO, FALSE, 0 (zero), or pressing the Return key.
o End the process: QUIT or Ctrl/Z
o 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 examples.)
3.4 /COPY_SOURCE
/COPY_SOURCE ddcu:
/COPY_SOURCE DSAn:
/COPY_SOURCE /ALL
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
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 dismounted.
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 successfully.
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
device.
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.
3.5 /DELETE
/DELETE DSAn:
/DELETE /NAME
Note: This qualifier applies to HBMM operations only. If you
specify any non-HBMM qualifiers with this one, the command will
fail.
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 DSA1:
$ SET SHADOW /DELETE DSA1 /POLICY=HBMM
In contrast, the following command removes COMPANY_POLICY from
the cluster:
$ SET SHADOW /DELETE /NAME=COMPANY_POLICY /POLICY=HBMM
You cannot delete the NODEFAULT policy.
You cannot specify /ALL with /DELETE.
3.6 /DEMAND_MERGE
/DEMAND_MERGE DSAn:
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
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 VSI 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
3.7 /DISABLE
/DISABLE=HBMM DSAn:
/DISABLE=HBMM /ALL
/DISABLE=SPLIT_READ_LBNS
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.
3.8 /ENABLE
/ENABLE=HBMM
/ENABLE=SPLIT_READ_LBNS
/ENABLE=HBMM enables host-based minimerge (HBMM) on the
specified shadow set or across the entire cluster if an
applicable HBMM policy exists. This value applies to HBMM
operations only. If you specify any non-HBMM qualifiers
with this value, the command will fail.
/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. To learn more
about HBMM policies and their application, see the VSI Volume
Shadowing for OpenVMS manual.
3.9 /EVALUATE
/EVALUATE=RESOURCES
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
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 restarted.
RESOURCES is the only supported value for /EVALUATE, and it must
be included.
/EVALUATE does not apply to MSCP-based minimerge operations.
MSCP-based minimerge operations are not subject to cancellation
and restart by /EVALUATE.
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.
3.10 /FORCE_REMOVAL
/FORCE_REMOVAL ddcu:
/NOFORCE_REMOVAL ddcu:
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
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 /FORCE_REMOVAL.
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.
3.11 /LOG
Instructs the volume shadowing software to Note: Do not include
any HBMM-specific qualifiers in a command with this qualifier;
doing so causes the command to fail.
display a brief message confirming that the SET SHADOW command
completed. If /OUTPUT is also specified, this information is
written to the output file.
3.12 /MEMBER_TIMEOUT
/MEMBER_TIMEOUT=n ddcu:
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
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.
3.13 /MVTIMEOUT
/MVTIMEOUT=n DSAn:
/MVTIMEOUT=n /ALL
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
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.
NOTE
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.
3.14 /NAME
/NAME=policy-name
Note: This qualifier applies to HBMM operations only. If you
specify any non-HBMM qualifiers with this one, the command will
fail.
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 VSI
Volume Shadowing for OpenVMS manual.
3.15 /OUTPUT
/OUTPUT=file-name
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
Outputs any messages to the specified file.
3.16 /POLICY
/POLICY=HBMM[=policy-name]
/POLICY=HBMM[=policy-specification]
Note: This qualifier applies to HBMM operations only. If you
specify any non-HBMM qualifiers with this one, the command will
fail.
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 VSI 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.
o MASTER_LIST=list
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:
MASTER_LIST=NODE1
MASTER_LIST=(NODE1,NODE2,NODE3)
MASTER_LIST=*
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:
(MASTER_LIST=(NODE1,NODE2), MASTER_LIST=(NODE3,NODE4))
There is no significance to the position of a system name in a
master list.
o COUNT=n
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 chosen.
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.
Examples:
(MASTER_LIST=(NODE1,NODE2,NODE3), COUNT=2)
(MASTER_LIST=(NODE1,NODE2,NODE3),COUNT=2),(COUNT=2,MASTER_LIST=(NODE4,NODE5,N
NODE6))
o RESET_THRESHOLD=n
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
VSI Volume Shadowing for OpenVMS manual.
The reset 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.
When the 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)
Example:
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) -
_$ /NAME=POLICY_2
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 help topic for several more
/POLICY examples. For more information about HBMM policies,
see the VSI Volume Shadowing for OpenVMS manual.
o MULTIUSE=n
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 copy
occurs.
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 copy operation.
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.
o DISMOUNT=n
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:
DISMOUNT/POLICY=MINICOPY
3.17 /PRIORITY
/PRIORITY=n DSAn:
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
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 system.
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.
3.18 /READ_COST
/READ_COST=n ddcu:
/READ_COST=n DSAn:
/READ_COST=n $n$DGAn:
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
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:
o DECram device
o Directly connected device in the same physical location
o Directly connected device in a remote location
o DECram served device
o 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 issued.
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 site 2.
3.19 /RECOVERY_OPTIONS
/RECOVERY_OPTIONS=DELAY_PER_SERVED_MEMBER=n
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
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 VSI Volume Shadowing for OpenVMS manual for more
information.
3.20 /RESET_COUNTERS
Note: This qualifier applies to HBMM operations only. If you
specify any non-HBMM qualifiers with this one, the command will
fail.
Resets the shadowing specific counters that are maintained for
each shadow set. These counters can be displayed using the SHOW
SHADOW command.
The counters that are reset to 0 are the following:
HBMM Reset Count
Copy Hotblocks
Copy Collisions
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 VSI Volume Shadowing for OpenVMS.
3.21 /SITE
/SITE=n ddcu:
/SITE=n DSAn:
Note: Do not include any HBMM-specific qualifiers in a command
with this qualifier; doing so causes the command to fail.
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
through 255.
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 configurations.)
3.22 /STALL
/STALL=WRITES[=nnn]
/NOSTALL=WRITES[=nnn]
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.
4 – Examples
1.$ ! Command sequence used on system 1 at site 1:
$ MOUNT/SYSTEM DSA0:/SHADOW=($1$DGA0:,$1$DGA1:) TEST
$ SET SHADOW/SITE=1 DSA0:
$ !
$ ! Command sequence used on system 2 at site 2:
$ MOUNT/SYSTEM DSA0:/SHADOW=($1$DGA0:,$1$DGA1:) TEST
$ SET SHADOW/SITE=2 DSA0:
$ !
$ ! Commands used on both system 1 and system 2:
$ SET SHADOW/SITE=1 $1$DGA0:
$ SET SHADOW/SITE=2 $1$DGA1:
In this example, the system at site 1 will perform reads from
$1$DGA0, which is located at that site, while the system at
site 2 will perform reads from $1$DGA1, which is located at
site 2.
2.$ SET SHADOW DSA1: /POLICY=HBMM= -
_$ (MASTER_LIST=(NODE1,NODE2,NODE3), COUNT=2, -
_$ RESET_THRESHOLD=75000)
This command defines an HBMM policy for shadow set DSA1:. The
policy specifies that no more than two systems of the three
systems listed can have an HBMM master bitmap. Once 75000
blocks have been modified on DSA1:, any existing HBMM bitmaps
are zeroed.
3.$ SET SHADOW /POLICY=HBMM=(MASTER_LIST= -
_$ (NODE1,NODE2,NODE3), RESET_THRESHOLD=75000, COUNT=2) -
_$ /NAME=HONESTY_IS_BEST
This command defines the named policy HONESTY_IS_BEST. This
policy is available to all cluster members, but is not applied
to any specific shadow set.
4.$ SET SHADOW DSA1: /POLICY=HBMM=HONESTY_IS_BEST
This command associates the named policy HONESTY_IS_BEST with
shadow set DSA1.
5.$ SET SHADOW /POLICY=HBMM=( -
_$ (MASTER_LIST=(NODE1,NODE2,NODE3), COUNT=2), -
_$ (MASTER_LIST=(NODE4,NODE5,NODE6), COUNT=2), -
_$ RESET_THRESHOLD=150000) -
_$ /NAME=POLICY_2
This command defines the HBMM named policy POLICY_2, which has
two master lists.
6.$ SET SHADOW DSA2: /POLICY=HBMM=POLICY_2
This command associates the named policy POLICY_2 with shadow
set DSA2.
7.$ SET SHADOW /POLICY=HBMM /DELETE /NAME=POLICY_2
This command deletes the named policy POLICY_2. Note that
any shadow set that had acquired the attributes of POLICY_
2 by execution of a SET SHADOW DSAn: /POLICY=HBMM=POLICY_2
command is not affected. Changes made to a named policy are
not retroactive to a mounted shadow set that was assigned the
characteristics of a previous version of that named policy.
8.$ SET SHADOW DSA1: /POLICY=HBMM /DELETE
This command deletes the existing HBMM policy from DSA1:. If
this HBMM policy is enabled on DSA1:, you must first execute
the following command to disable the policy before you can
delete it:
$ SET SHADOW DSA1: /DISABLE=HBMM
9.$ SET SHADOW /DEMAND_MERGE/CONFIRM
Allow merge of _DSA721:? [N]:y
Allow merge of _DSA850:? [N]: TRUE
Allow merge of _DSA1010:? [N]:N
$
In this example, a merge operation is initiated on DSA721: and
DSA850: but not on DSA1010:.
10$ SET SHADOW DSA1/POLICY=HBMM=(MASTER=*,COUNT=12,MULTIUSE=12,DISMOUNT=1)
In this example, a policy is set in which all 12 bitmaps can
be used as multiuse bitmaps. When you execute the command
DISMOUNT/POLICY=MINICOPY, 1 minimerge bitmap is converted to
multiuse bitmap. You can use this multiuse bitmap with the
MINICOPY command to add the dismounted member back to the
shadow set. In other words, it specifies that 12 bitmaps can
be used during the automatic and 1 bitmap during the manual
removal of the shadow set member.
11$SET SHADOW DSA42 /STALL=WRITES
In this example, the writes are stalled to the shadow set for a
period of SHADOW_MBR_TMO seconds.
12$SET SHADOW DSA42 /STALL=WRITES=60
In this example, the writes are stalled to the shadow set for a
period of 60 seconds.
13$SET SHADOW DSA42 /NOSTALL=WRITES=30
In this example, the writes are allowed to the shadow set after
a period of 30 seconds.