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HP OpenVMS DCL Dictionary

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Changes the characteristics of one or more mounted Files-11 volumes. The SET VOLUME command affects only the node on which the command is issued, and will not affect any other nodes, even when a volume is mounted on multiple nodes in an OpenVMS Cluster configuration.

If you are not the owner of the volume, requires control access to the volume.


SET VOLUME device-name[:][,...]



Specifies the name of one or more mounted Files-11 volumes.



Requires OPER (operator) privilege.

Specifies the number of directories to be maintained in system space for ready access. You can specify a value n in the range of 0 to 255. If you specify the qualifier /ACCESSED and omit the number of directories, a default value of 3 is used. If you specify a value greater than the current value, the new value is effective immediately; otherwise, the new value is not effective until the next time the volume is mounted.


Defines a default for data check operations following all read and write operations to the specified volume. (If you do not specify the /DATA_CHECK qualifier, no checks are made.) Keywords are as follows:
[NO]READ Performs checks following all read operations.
[NO]WRITE Performs checks following all write operations (default).



Determines whether the space occupied by a file is overwritten with a system-specified pattern when a file on the volume is deleted.


Specifies the number of blocks to be used as a default extension size for all files on the volume. You can specify a value n in the range of 0 to 65,535. If you specify the /EXTENSION qualifier without specifying a value, a default value of 0 (the OpenVMS RMS default) is used.

For example, during an update operation, the extension default is used when a file increases to a size greater than its initial default allocation.


Sets the default protection to be applied to all files on the specified disk volume. Specify the ownership parameter as system (S), owner (O), group (G), or world (W) and the access parameter as read (R), write (W), execute (E), or delete (D). A null access specification means no access.


This attribute is not used while the volume is in use on an OpenVMS system, but the attribute is provided to control the process use of the volume on RSX-11M systems. The OpenVMS system always uses the default file protection; the protection can be changed with the DCL command SET PROTECTION/DEFAULT.



Determines whether the file highwater mark (FHM) volume attribute is set. The FHM attribute guarantees that a user cannot read data that was not written by the user. Applies to Files-11 On-Disk Structure Level 2 (ODS-2) and 5 (ODS-5) volumes only.


Specifies a 1- to 12-character ANSI name to be encoded on the volume. The specified label remains in effect until it is changed explicitly; dismounting the volume does not affect the label. HP strongly recommends that a volume label should consist of only alphanumeric characters, dollar signs ($), underscores (_), and hyphens (-).


Changing the volume label does not change other structures that used the original volume label. For example, the DISK$label logical volume name is not changed nor is the device-lock name that is kept internally by OpenVMS. As a result, if you attempt to access another disk that has the same volume label as the original volume of this device, you may get error messages such as the following: "%MOUNT-F-VOLALRMNT, another volume of same label already mounted".

HP recommends that, if you change a disk volume label, you also dismount and remount the disk on all nodes in the cluster so that the names and locks are consistent.

If you change the volume label on a nonsystem disk and the PRODUCT INSTALL command has been used to install software products on that disk, you must update the software product database to reflect this change. To accomplish this, first dismount and remount the disk. Then use the PRODUCT REGISTER VOLUME command to replace all occurrences of the old DISK$label with the new logical volume name that was created by the MOUNT command.


You do not need to take this action when you change the label of the system disk. The POLYCENTER Software Installation Utility continues to use the old logical volume name until the system is rebooted. After reboot (when the system disk is remounted), the utility automatically identifies the system disk using its new logical volume name.


Specifies that the volume is to be enabled for volume expansion. n specifies the upper limit of the expansion (in blocks). If no value is specified, the maximum expansion potential is set up.

The maximum expansion size depends on the cluster size defined for the volume using the INITIALIZE/CLUSTER_SIZE command. If the cluster size is 8 or more, the current maximum expansion supported on OpenVMS (1TB) is set up. If the cluster size is less than 8, the expansion limit is set to 65535*4096*Cluster-size because the maximum size of the bitmap is 65535 blocks. For more information about volume expansion, see the HP Volume Shadowing for OpenVMS manual.

This command must be executed while the disk is mounted privately.

If you add additional physical storage in the future, you can use the /SIZE qualifier to increase the volume size.


/NOLOG (default)

Determines whether the volume specification of each volume is displayed after the modification.



Determines whether mount verification is enabled. Mount verification prevents interruption to user input/output operations and notifies the operator of problems with the disk.


Sets the owner user identification code (UIC) of the volume to the specified UIC. The default UIC is that of the current process. Brackets ([]) are required around the UIC. Specify the UIC by using standard UIC format as described in the HP OpenVMS Guide to System Security.


Specifies the protection to be applied to the volume. The following rules apply:
  • Specify the ownership parameter as system (S), owner (O), group (G), or world (W).
  • Specify the access parameter as read (R), write (W), create (C), or delete (D).

The default protection is all types of access by all categories of user.


Recovers caching limits for a volume that was dismounted improperly. If a disk volume was dismounted improperly (such as during a system failure), and was then remounted with the MOUNT/NOREBUILD command, you can use SET VOLUME/REBUILD to recover the caching that was in effect at the time of the dismount. The FORCE option forces the disk to be rebuilt unconditionally, thus updating the free block count in the disk volume's lock value block.


Specifies the minimum and maximum retention times to be used by the file system to determine the expiration date for files on the volume. When a file is created, its expiration date is set to the current time plus the maximum time. Each time the file is accessed, the current time is added to the minimum time. If the sum is greater than the expiration date, a new expiration date is computed.

If you omit the maximum value, a default value that is the smaller of (2 x min) or (min + 7) days is used. For example, /RETENTION=3- is the same as /RETENTION=(3-,6-), while /RETENTION=10- is the same as /RETENTION=(10-,17-).

The command SET VOLUME/RETENTION=0 disables retention times on the volume.


Specifies the amount of disk space (in blocks) that is usable for the file system. This value must be greater than the current logical volume size and less than or equal to the physical size of the disk or the expansion limit (specified by /LIMIT), whichever is smaller.

If the value is omitted, the usable space is increased to the physical size of the disk or the expansion limit, whichever is smaller.


Sets the structure level of the volume. Use the value 5 to set the volume to ODS-5.

When the /STRUCTURE_LEVEL qualifier is used with other qualifiers, the volume structure level is set prior to the other qualifiers being performed.

You cannot use the SET VOLUME command to change a volume from ODS-5 to ODS-2. To reset a volume to ODS-2, see the instructions in the HP OpenVMS System Manager's Manual, Volume 1: Essentials.



Enables the processing of subsystem ACEs. Requires the SECURITY privilege. By default, the disk from which you boot has protected subsystems enabled but other disks do not. For further details on subsystems, see the HP OpenVMS Guide to System Security.

/UNLOAD (default)


Specifies whether the volume is unloaded (spun down) when the DCL command DISMOUNT is entered.


Specifies a user name of up to 12 alphanumeric characters to be recorded on the volume. The default name is the current process user name.


Enables or disables hardlinks and automatic updates of access dates on ODS-5 volumes.

To limit the performance impact if a file is accessed frequently, you can suppress update of the access time if the change is small. A delta time is used to determine when a new access time is significant. The default value for delta-time is 1 second, chosen to comply with the "seconds since EPOCH" time interface required by POSIX st_atime . A site can choose a larger delta time to reduce overhead if 1-second granularity is not required.

To disable access date support on a volume, use the SET VOLUME/VOLUME_CHARACTERISTICS=NOACCESS_DATES command. This command affects only the node on which the command is issued. Other nodes are not affected by the change until the next time the volume is mounted.

For additional information about ODS-5 volumes, see the Guide to OpenVMS File Applications and to the sections about File Service Extensions in the OpenVMS Alpha Version 7.3--1 New Features and Documentation Overview. This archived manual is on the OpenVMS documentation Web site:


Click on "Archived documents" in the left sidebar to link to this manual.


Specifies the number of mapping pointers to be allocated for file windows.

The value of n can be from 7 to 80; the default value is 7.



This qualifier only affects applications such as PATHWORKS that can request deferred writes to file headers. You use it to control whether these applications can use the deferred write feature.

Use /NOWRITETHROUGH to allow these applications to use the deferred write feature. When one of these applications explicitly requests a deferred write when updating a file header, control returns to the application when the I/O request has been queued; the application does not have to wait until the data is on disk.

Note that although the SHOW DEVICES/FULL command shows the volume status as write-back caching enabled, the extended file cache (XFC) will still be in write-through mode.

Use /WRITETHROUGH to disable the deferred write feature, so that no applications can use it. The SHOW DEVICES/FULL command shows the volume status as write-through caching enabled.

The deferred write feature is not available on Files-11 ODS-1 volumes.




The SET VOLUME command in this example requests that data checks be performed following all read and write operations to DKA5.



The SET VOLUME command in this example sets the default protection to be applied to all files created on volume DKA5. System (S) and owner (O) are granted all types of access; group (G) and world (W) are permitted only to read and execute files on DKA5.



The SET VOLUME command in this example encodes the label LICENSES on the volume DKA5. Note that if characters in labels are entered in lowercase, they are changed to uppercase by the /LABEL qualifier.



The SET VOLUME command in this example specifies that 25 directories are to be maintained in system space for ready access for the volume DKA0. The command also assigns the user name MANAGER to the volume and displays the volume specification after the volume is modified.



The SET VOLUME command in this example causes a rebuild operation to begin on the volume that is mounted on NODE$DKA2. The /LOG qualifier directs the SET VOLUME command to display a notification message.


$ MOUNT $252$DUA716: TST716


This example shows how to increase the expansion limit of a volume mounted in a cluster.



This command disables hard links on SYS$DISK.

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