Document revision date: 19 July 1999

When planning disk volume sets, keep in mind the following points:

• You can turn any single volume into a volume set by binding it with a newly initialized volume. Likewise, you can add another newly initialized volume to an existing volume set.
• Do not include a system disk in a volume set.

  Caution Do not make the system disk part of a volume set because updates, upgrades, and optional product installations do not install correctly, and the operating system will no longer boot successfully.

• You cannot bind two existing separate volumes containing files into a volume set. (The MOUNT command appears to let you do this, but the result is not a coherent volume set.)
• Enter the MOUNT/BIND command only once to bind a volume set; thereafter, the volume set association is recorded on the volumes. (See Section 8.5 for details.)
• Once you bind two or more volumes into a volume set, you cannot separate them. The only way to separate a volume set is to use the Backup utility (BACKUP) to copy sets of directories selectively. (See Section 10.13 for more information.)

When you mount a disk volume set, the volume label specified in the list must correspond to a device name in the same position in the device name list.

You can bind two or more disk volumes into a volume set. The first volume in the set is called the root volume. Each volume in the set is identified by a volume number relative to the root volume, which is always relative to volume 1.

A disk volume set has a single directory structure. The master file directory (MFD) is on the first volume in the set.

When a disk volume set is on line and mounted, you can access all files and directories in the set by specifying either of the following names:

• Device name of the device on which the root volume is mounted
• Logical name assigned to the volume set when it was mounted

Use the /BIND qualifier with the MOUNT command to create a disk volume set in the following format:

MOUNT/BIND=volume-set-name

where:

volume-set-name

Specifies a 1- to 12-alphanumeric-character name identifying the volume set.

The volume set name must be different from all volume labels within the set, and all labels in the set must be unique.

The /BIND qualifier identifies a volume set by assigning it a volume set name that applies to all volumes in the set. The qualifier also identifies the root volume and creates the directory structure for the volume.

When you create files on a volume set, the file system allocates space for the files anywhere on the set, wherever the most space exists. When existing files on any volume are extended, extension occurs on the same volume unless the volume is physically full.

You can add new volumes to a volume set whenever additional space is needed. You can, for example, bind all disk volumes that are mounted into a volume set on a daily basis. Since this set contains all user file directories, users do not need to specify device names in file specifications to access files on any volume in the volume set. In fact, the physical location of a file is of no concern to users of the system.

You do not need special privileges to create volume sets. However, you must have write access to the index file on all volumes you are attempting to bind into a volume set; this usually means you also must have a system UIC, have the user privilege SYSPRV, or be the owner of the volumes.

The following sections explain how to perform these tasks:

Task	Section
Create a disk volume set from new volumes	Section 8.6.2
Create a shadowed disk volume set	Section 8.6.3
Create a disk volume set from an existing volume and a new volume	Section 8.6.4
Add volumes to an existing disk volume set	Section 8.6.5

8.6.2 Creating a Disk Volume Set from New Volumes

To create a disk volume set from new disk volumes:

1. Allocate the necessary devices and physically load the volumes.
2. Initialize each volume in the set.
   When you initialize volumes for a volume set, you can use qualifiers with the INITIALIZE command to define the volume ownership and protection. Protection and ownership information is obtained from the root (first) volume. The protection and ownership of the other volumes is ignored.
3. Enter the MOUNT/BIND command to create the volume set. The MOUNT/BIND command both creates the volume set and mounts the volumes. When this command completes successfully, all volumes in the set are ready for use; in other words, you can now create user file directories.
4. Use the /BIND qualifier only once to create the volume set. Subsequently, you can mount the volume set with a single MOUNT command.

Examples

1. $ INITIALIZE DUA1: PAYVOL1 $ INITIALIZE DUA2: PAYVOL2 $ INITIALIZE DUA3: PAYVOL3 $ MOUNT/BIND=MASTER_PAY DUA1:, DUA2:, DUA3: PAYVOL1,PAYVOL2,PAYVOL3

   
   This example assumes that the volumes to be bound contain no files or data. The INITIALIZE command initializes each volume in the set. The MOUNT/BIND command defines the volume set name, MASTER_PAY, and defines the relative volume numbers of the volumes PAYVOL1, PAYVOL2, and PAYVOL3.
   The order of the device names corresponds to the volume labels specified: PAYVOL1 must be physically loaded on DUA1:, PAYVOL2 on DUA2:, and PAYVOL3 on the DUA3: device.
   PAYVOL1, which is listed first in the list of labels, becomes the root volume of the set. The master file directory (MFD) for PAYVOL1 contains the directory structure for the entire volume set.

2. $ MOUNT DUA1:,DUA2:,DUA3: PAYVOL1,PAYVOL2,PAYVOL3

   
   This example illustrates the use of one MOUNT command to mount a previously created volume set.

The following example illustrates one way to create a shadowed volume set.

$ MOUNT/BIND=TEST3013 DSA3011/SHADOW=($1$DUA402:,$1$DUA403:), DSA3012/SHADOW=($1$DUA404:,$1$DUA405:) TEST3011,TEST3012 TEST3013

This command creates a volume set with the logical name TEST3013. The volume set TEST3013 is shadowed, and each element of the shadowset (TEST3011 and TEST3012) is itself a volume set.

8.6.4 Creating a Disk Volume Set from an Existing Volume and a New Volume

To create a disk volume set from an existing volume and a new volume:

1. Use the DISMOUNT command to dismount the existing volume. Use the /NOUNLOAD qualifier to logically dismount the volume from the drive. (The volume, however, remains physically loaded on the drive.)
2. Use the INITIALIZE command to initialize the new volume, specifying the device on which the volume is to be mounted and the volume label.
3. Use the MOUNT/BIND command to bind the new volume to the existing volume, specifying the volume set name, the devices on which the volumes are mounted, and the volume labels.
   Specify the volume label of the existing volume first; it becomes the root volume of the set. When you create a volume set from an existing volume, you must specify the label of the existing volume first because the file system must build on the existing directory structure.

Example

The following example shows how to create a disk volume set (called USERS) from an existing volume. In this example, the volume USERFILES already contains a directory structure and files; the volume is currently located on the DUA1: device.

$ DISMOUNT/NOUNLOAD DUA1: $ INITIALIZE DUA2: USERFILES2 $ MOUNT/BIND=USERS DUA1:, DUA2: USERFILES, USERFILES2

In the MOUNT/BIND command, you must specify the existing volume label USERFILES before the volume label USERFILES2. USERFILES will be the root volume of the set.

You can add volumes to an existing volume set at any time. The maximum number of volumes in a volume set is 255.

This section contains examples that show how to add volumes to an existing volume set.

Examples

1. $ INITIALIZE DUA4: PAYVOL4 $ MOUNT/BIND=MASTER_PAY DUA4: PAYVOL4

   
   In this example, the volume set named MASTER_PAY is on line and mounted and has volumes named PAYVOL1, PAYVOL2, and PAYVOL3.
   The MOUNT/BIND command binds the volume PAYVOL4 with the existing volume set and makes the volume ready and available for use. Note that, if the volume set MASTER_PAY is mounted with the /SYSTEM, /GROUP, or /SHARE qualifier, the MOUNT/BIND command that adds a volume to the set must also specify the appropriate qualifier.
   When you add a volume to an existing set, the only volume in the set that you must mount is the root volume, relative volume 1 (in this example, DUA4:). Mounting any of the other volumes is not necessary.

2. $ INITIALIZE DUA4: PAYVOL4 $ MOUNT/BIND=MASTER_PAY DUA1:, DUA2:, DUA3:, DUA4: - _$ PAYVOL1, PAYVOL2, PAYVOL3, PAYVOL4/SYSTEM

   
   In this example, a set named MASTER_PAY already exists, with volumes named PAYVOL1, PAYVOL2, and PAYVOL3.
   You can add a volume to a set at the same time that you mount the volume set, as this example shows. Note that the first device/volume pair listed in the MOUNT/BIND command is the root volume of the set, the DUA1: volume. When you add a volume to a set while mounting the set, you must list the root volume first.

To access an ISO 9660-formatted CD-ROM, you can mount disk volumes in two ways:

• Directly, using the Mount utility (MOUNT)
• Indirectly, using the DCL command MOUNT

The Mount utility (MOUNT) builds the I/O database structures that are needed to access ISO 9660 directories and files. MOUNT also verifies the presence of an appropriate ACP to perform $QIO functions specific to ISO 9660. Currently, you cannot mount ISO 9660 media as a system disk. Refer to the OpenVMS System Management Utilities Reference Manual for details.

For more information about ISO 9660 volume structure on CD-ROM media, refer to the Guide to OpenVMS File Applications.

8.7.1 Mounting ISO 9660 Volume Sets

ISO 9660 supports volume sets of up to 65,535 volume set members. At any one time, users can mount a 255-member subset of the total volume set of 65,535.

If your volume set is greater than the number of CD-ROM readers available to you, you can swap volume set members, for example, as you might when you have a single reader with multiple volume set members.

8.7.2 Mounting ISO 9660 Volume Groups

A volume group consists of one or more consecutively numbered volumes within a volume set. Affinity between the members of a volume group is established by the fact that the volumes are recorded together and are subject to the same maximum-volume-set-size parameter.

Each volume in a volume group contains information describing all the files and directories recorded on all of the volumes in the volume set, up to and including the members of its volume group. For example, assume that a volume set includes two volume groups:

• The first group includes Volumes 1 and 2, which were recorded together, prior to the second group.
  Volumes 1 and 2 each contain information only about their volume group; they have no information about the volumes in the second volume group.
• The second group includes Volumes 3, 4, and 5, which were recorded together at a later date.
  Volumes 3, 4, and 5 each contain information about all of the volumes in the volume set, including Volumes 1 and 2.

How to Perform This Task

When you mount a volume set, you must first mount a member of the highest-numbered volume group (the most recently recorded group---in the example, Volume 3, 4, or 5), because only a member of the highest-numbered group has the information needed to mount all members of the volume set.

If you do not follow this requirement, you must dismount all of the volumes and start again by specifying a member of the highest-numbered volume group as the first volume to be mounted.

8.7.3 Handling Partially Mounted ISO 9660 Volume Sets

OpenVMS systems support partially mounted ISO 9660 volume sets. Data is usually read from all mounted volumes in a manner that is transparent to the user program.

When a volume-set member is not mounted because the volume set is partially mounted, OPCOM sends a message to the OPERATOR class DISK requesting that the unmounted volume be mounted. If you do not honor the request within a specified time period, or if you do not enable the option to provide for dynamically mounting a volume, the I/O process fails, and an error message is issued.

8.7.4 Mounting ISO 9660 Volumes Using SVDs

All ISO 9660 volumes contain a Primary Volume Descriptor (PVD) that uses ASCII (ISO 646-IRV) as the character set. Both ISO 9660 and OpenVMS file naming conventions use the same subset of ASCII characters when displaying the directories and file names of a volume.

In addition to mounting ISO 9660 volumes using the default PVD, you can also mount ISO 9660 volumes using a Supplementary Volume Descriptor (SVD).

This capability allows access to an ISO 9660 volume with directories and file names containing characters from character sets other than the ISO 9660 limited set, which includes only A through Z, underscore (_), period (.) and semicolon (;).

The author of the ISO 9660 volume set must record the volume with the required PVD, and optionally with one or more SVDs. Each SVD must contain a unique volume label and escape sequence.

Use the following command syntax to mount an ISO 9660 device using an SVD:

MOUNT device-name volume-label /UCS_SEQUENCE=escape_sequence

where:

device-name	Specifies the physical device name or logical name of the device on which the ISO 9660 volume is to be mounted.
volume-label	Specifies the SVD volume label obtained from the author's label on the CD-ROM.
escape-sequence	Specifies the escape sequence obtained from the author's label on the CD-ROM.

If an ISO 9660 volume contains SVDs with no escape sequence specified, the default character set is assumed to be ISO 646 (ASCII). This default character set allows the use of the file specification character set supported by OpenVMS, which includes these additional characters: dollar sign ($) and dash (-).

Use the following command syntax to mount a volume using the SVD volume label when no escape sequence is specified:

MOUNT device-name volume-label /UCS_SEQUENCE=""

Refer to the Guide to OpenVMS File Applications for more information about ISO 9660 volume structure on CD-ROM media.

8.7.5 Handling ISO 9660 Restrictions

Table 8-15 describes problems and restrictions that apply to OpenVMS support of the ISO 9660 standard and explains how to resolve them.

Table 8-15 ISO 9660 Restrictions

Media Affected	Description and Resolution
Volume Labels	These can contain from 1 to 32 characters. The first 12 characters are used to produce a unique volume identity. If the label is not unique within the first 12 characters, the volume will not mount and the following error message is displayed: %SYSTEM-F-VOLALRMNT, another volume of the same label already mounted How to resolve this problem: Mount the volume specifying a different volume label and use the /OVERRIDE=IDENTIFICATION qualifier. This will override the volume's label so as not to conflict with the label of an already-mounted volume.
Volume Set Labels	These can be from 1 to 128 characters in length. The first 12 characters are used to produce a unique volume set identity. If the volume set label is not unique within the first 12 characters, the volume will not mount and one of the following error messages will be displayed: %SYSTEM-F-VOLINSET, volume is already part of another volume set %MOUNT-F-DUPRVN, duplicate volume number already mounted How to resolve this problem: Mount the volume specifying a new volume set label with the /BIND= volume-set-name command qualifier.
Volume Label and Volume Set Label Duplication	The first 12 characters of both the volume label and the volume set label are used to produce different lock manager resource names, which are then used to coordinate volume and volume set associations. If both the volume label and the volume set label are the same (within the first 12 characters, including null labels), a lock manager deadlock error occurs and the following error message is displayed: %SYSTEM-F-DEADLOCK, deadlock detected How to resolve this problem: Mount the volume specifying a different volume label and use the /OVERRIDE=IDENTIFICATION command qualifier. This will override the volume's label so as not to conflict with the volume set's label.
Undefined Record Format Errors	Many ISO 9660 CD-ROMs are mastered without a specified record format because the ISO 9660 media can be mastered from platforms that do not support the semantics of files containing predefined record formats. OpenVMS file system utilities (such as TYPE and COPY), language RTLs, and applications that use RMS for record access may report RMS errors, utility errors, and language errors when accessing files whose record format is undefined or appears illegally specified. How to resolve this problem: Use the following command syntax at mount time to force all files of type UNDEFINED to the STREAM record format having a maximum record length of 512 bytes: MOUNT/MEDIA=CDROM/UNDEFINED=(STREAM:512) device label For more information about RMS record formatting, refer to the OpenVMS Record Management Utilities Reference Manual and the OpenVMS Record Management Services Reference Manual.

8.8 Mounting Tape Volume Sets

The procedure for mounting a tape volume set is similar to the procedure for mounting a single tape volume, described in Section 8.5. The number of volume identifiers does not need to equal the number of device names you specify. In other words, when you mount a tape volume set, you can specify more volume identifiers than device names or more device names than volumes.

The number of devices you specify directly affects the action taken by the tape file system when processing continuation volumes in a volume set. For example, when the number of devices is greater than the number of volumes, the tape files system requests a continuation volume to be mounted on the first drive from the list that does not have a volume mounted.

When mounting a volume set, make sure that all the volumes in the set contain write rings if the user intends to write to any of the volumes in the set. (If even one of the volumes in the set does not contain a write ring at mount time, all volumes are write-locked; the system is unable to write to any of them.) Load the volumes on the drives that have been allocated and place the drives on line.

The following sections explain how to perform these tasks:

Task	Section
Create a tape volume set	Section 8.8.1
Mount continuation volumes in a volume set	Section 8.8.2
Mount volume sets with automatic switching disabled	Section 8.8.2.3

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