Managing Types of Volume Sets

Disk management includes knowing types of volume sets, system and nonsystem, and being able to create volume set account structures. With disk management, you can manage disk space to maximize efficiency and be able to reinitialize a disk volume when it becomes obsolete.

The operating system requires the presence of the system volume set MPEXL_SYSTEM_VOLUME_SET to boot and run the system. You may also define other volume sets, called nonsystem volume sets. You can boot the system and use it even when nonsystem volume sets have been removed.

Some differences between the system and nonsystem volume sets are important to remember.

Table 9-1 System and Nonsystem Volume Sets

System Volume Set	Nonsystem Volume Set
Name must be `MPEXL_SYSTEM_VOLUME_SET`	Name can be whatever you wish, 32 or fewer alphanumeric characters.
Always mounted when the system is running. May be partially mounted.	Does not need to be mounted when the system is running.
Allows permanent and transient storage.	Allows permanent storage only.
Master contains system image and configuration.	Partitions user data into separate entities.
Master must be present to boot the system.	Requires the master to be present to use the set.
Master contains XM log file.	Master contains XM log file.

It is also helpful to remember these features of volume sets:

Every volume set has a master volume, which is the only volume needed to define a volume set. It contains the configuration data, the root directory, a free space map, file label table, and a volume label with a unique volue set ID for the volume set.
Nonsystem volume sets are sometimes called mountable volume sets since they are not required for the system to run.
Transient storage is disk space used by the operating system.
Permanent storage is disk space reserved for user and operating system files and programs. Nonsystem volumes should only have permanent storage. No percentage of the volume should be allocated to transient storage.
You may use VOLUTIL to add additional system and nonsystem volumes while the system is running. Refer to the Volume Management Reference Manual (32650-90045) for more information.

To manage master and member volumes

The definition of a volume set is stored on the master volume rather than in a system table on the system volume set; the system only has information about mounted volume sets. The master volume of a volume set must be mounted before you can access files on other volumes in the set.

Figure 9-1 shows a master volume with two member volumes in the volume set named PROD.

Figure 9-1 Master and Member Volume

LDEV 1 is the disk pack or master volume of the system volume set, MPEXL_SYSTEM_VOLUME_SET. It must be mounted for the operating system to function.

A volume set name can contain up to 32 characters, including letters, numbers, underbar characters, and periods. The first character must be alphabetic.

A file cannot be spread across or span multiple volume sets. All volumes in a volume set should be mounted at the same time.

Accounts can span volume sets, but a group is contained within one volume set known as the home volume set. All groups have a home volume set (see the LISTGROUP command) that specifies on which volume set the files of any given group are to be found. A file's extents may be spread across the volumes within a volume set.

A class is a group of volumes within a volume set used to partition data. Files can be restricted to a particular volume class or volume by using the HPFOPEN intrinsic or the :BUILD command (with the ;DEV parameter.) Refer to the MPE/iX Intrinsics Reference Manual (32650-90028) for more information. Figure 9-2 illustrates an example of data partitioning with classes. A class name can contain up to 32 characters, including letters, numbers, underbar characters, and periods. The first character must be alphabetic.

Figure 9-2 Data Partitioning with Classes

Using classes is optional. When you create a new volume set, volume management assigns all volumes in the set to the default class DISC. You can specify another class, but the DISC class is necessary for MPE V/E and MPE/iX compatibility.

To display information about all mounted volumes

You can use CI command DSTAT within VOLUTIL to display information on all mounted volumes. To use it, enter a colon before entering DSTAT at the VOLUTIL prompt. DSTAT has the following parameters:

DSTA [[ldev] [ALL]]

To check nonsystem volumes

To use VOLUTIL to display the status of nonsystem volumes, enter:


  volutil::DSTAT

You'll see each volume listed by its LDEV number and type, something like the information in Example 9-1, below, which shows the status of three volumes.

Figure 9-3 Example 9-1. Displaying Volume States


   :dstat
     LDEV-TYPE   STATUS    VOLUME (VOLUME SET  -  GEN)
    ----------  --------  -----------------------------
     3- 079370   MASTER     MEMBER1     (DISKDUMP_VOLUME_SET-0)
     4- 079370   MEMBER     MEMBER2     (DISKDUMP_VOLUME_SET-0)
     5- 079370   SCRATCH 
    14- 079370   SCRATCH

The following list defines the five status categories you may see when you issue the DSTAT command:

MASTER: An accessible volume that contains volume set definition and data.
MEMBER: An accessible volume that contains only data.
LONER: An inaccessible volume that is closed or has no master. A volume has loner status if its master is not mounted, if it has been taken offline with the VSCLOSE command, or if it is a duplicate of another volume that is currently online.
SCRATCH: An inaccessible volume that is marked as having no valid data.
UNKNOWN: An inaccessible volume that is uninitialized or has an unrecognizable label. A volume has an unknown status if it does not have a label that the operating system can recognize. The volume could be a new disk pack, a volume that has been formatted, or a disk pack from another system. For example, if an MPE V/E private volume is mounted on an MPE/iX system, it is not recognized and is given an unknown status. You can initialize a volume that has an unknown status.

To check nonsystem volumes

To use VOLUTIL to display the status of nonsystem volumes, enter a colon (:) and the command DSTAT at the volutil prompt:


   volutil::DSTAT

You'll see each volume listed by its LDEV number and type, something like the information in Example 9-1, below, which shows the status of three volumes.

Figure 9-4 Example 9-1. Displaying Volume States


   :dstat
     LDEV-TYPE   STATUS    VOLUME (VOLUME SET  -  GEN)
    ----------  --------  -----------------------------
     3- 079370   MASTER     MEMBER1     (DISKDUMP_VOLUME_SET-0)
     4- 079370   MEMBER     MEMBER2     (DISKDUMP_VOLUME_SET-0)
     5- 079370   SCRATCH
    14- 079370   SCRATCH

To check all volumes

To check the status of both system and nonsystem volumes on the system, enter a colon (:) and the DSTAT ALL command at the volutil prompt.


   volutil:DSTAT ALL

DSTAT displays information about volumes that are mounted. If you have defined a volume but not initialized it, it will not appear in the display.

Figure 9-5 Displaying Mounted Volume Information


   volutil: :dstat all

   LDEV-TYPE STATUS  VOLUME       (VOLUME SET - GEN)
   --------- ------  ------------------------------------
   1-079350  MASTER  MEMBER1      (MPEXL_SYSTEM_VOLUME_SET-0)
   2-079350  MEMBER  MEMBER2      (MPEXL_SYSTEM_VOLUME_SET-0)
   3-079350  MEMBER  MEMBER3      (MPEXL_SYSTEM_VOLUME_SET-0)
   18-079350 MASTER  PRODMASTER   (PROD-0)
   25-079350 MEMBER  PRODMEMBER1  (PROD-0)

Managing Types of Volume Sets

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To manage master and member volumes

To display information about all mounted volumes

To check nonsystem volumes

To check nonsystem volumes

To check all volumes