HP OpenVMS Systems Documentation

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OpenVMS System Manager's Manual

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A.3.1.1 Boot Block

Block 0 on a system disk is the boot block. It contains the location and size of the primary bootstrap image, which is used to boot the system. Certain processors, in order to boot, must read this boot block to obtain the location of the bootstrap image. For more details, see Section 4.7.

A.3.1.2 Home Block

The home block is normally the next block after the boot block; it identifies the disk as a Files-11 volume. If for some reason the home block cannot be read (physically unusable), an alternative block will be selected for use as the home block. This block provides specific information about the volume and default values for files on the volume. Items in the home block include the following ones:

  • The volume name
  • Information to locate the remainder of the index file
  • The maximum number of files that can be present on the volume at any one time
  • The user identification code (UIC) of the owner of the volume
  • Volume protection information (specifies which users can read or write the entire volume)

Files-11 volumes contain several copies of the home block to ensure against accidental destruction of this information and the consequent loss of access to files on the volume.

A.3.1.3 File Headers

Most of the index file consists of file headers; each file header describes a portion of a file on the volume. File headers contain information such as the owner UIC, protection code, creation date and time, and access control lists (ACLs). Most importantly, the file header contains a list of extents that make up the file, describing where the file is logically located on the volume. If a file has a large number of extents, multiple file headers may be used to describe them. A file identifier number is associated with each file header.

When you create a file, you normally specify a file name to OpenVMS RMS, which assigns this name to the file on a Files--11 volume. OpenVMS RMS places the file name and file identifier associated with the newly created file into a directory, which contains an entry defining the location for each file. When you access the file, you supply the file name, which supplies a path to the file identifier through the directory entry. The file identifier, in turn, points to the location of the file header, which contains a listing of the extent or extents that locate the actual data.

Because they represent the current state of file storage on a volume, file headers are of particular interest to ANALYZE/DISK_STRUCTURE. Each file on a Files-11 disk (INDEXF.SYS included) is identified and located by a primary header (and extension headers, if required) in INDEXF.SYS.

Each fixed-length header contains both constant and variable-length data. This data is stored in one of the six areas shown in Table A-3.

Table A-3 Areas of Data in File Headers
Area of Data Description
Header This area contains the header identification, the file number and its sequence number, the protection code for the file, and offsets to the other file header areas.
Ident This area contains the identification and accounting data for the file (for example, the name of the file, its creation date and time, and backup date and time).
Map This area contains a list of retrieval pointers that map the virtual blocks of the file to the logical blocks of the volume. Each pointer describes one group of consecutively numbered logical blocks that is allocated to the file. Retrieval pointers are arranged in the order of the virtual blocks they represent.
Access control list An optional area that contains ACL-related information.
Reserved This area is reserved for use by special applications.
End checksum The last two bytes of the file header contain a 16-bit additive checksum of the preceding 255 words of the file header. The checksum helps verify that the block is a valid file header.

A set of contiguous clusters is known as an extent. The size of an extent varies according to the number of contiguous clusters. For example, assume a file requires 1000 blocks of storage, and the file system finds a set of 800 contiguous blocks and a set of 200 contiguous blocks. The file would then be stored in two extents: one consisting of 800 blocks, the other of 200.

The primary header of a file points to the first extent of that file and to as many extents as can be stored in the map area of the primary header. When the number of extents required to contain a file exceeds the map area available in the primary header, or the ACL is too large to fit in the primary header, the file is allocated an extension header. Extension headers contain all the constant data of the primary header, as well as the variable data (in the header map area and access control list) that specifies the locations of the extents to which the extension header points.

ANALYZE/DISK_STRUCTURE confirms the validity of a file by working its way down the list of primary and extension headers of the file. During this process, ANALYZE/DISK_STRUCTURE checks the validity of the file header, the chain of pointers to all extension headers, the retrieval pointers in all headers, and the attributes of the file.

A.3.2 Storage Bitmap File, BITMAP.SYS

The storage bitmap file is a contiguous file that the file system uses to keep track of the available space on a volume. This file contains a storage control block (SCB), which consists of summary information intended to optimize the Files--11 space allocation, and the bitmap itself, which lists the availability of individual blocks.

The SCB contains summary information about the volume (cluster factor, volume size, blocking factor, and so forth). Each bit in the bitmap represents an allocatable cluster on the volume. If a bit is set, the corresponding cluster is available for use. If a bit is clear, the cluster is not available.

During normal operation, the operating system moves portions of the bitmap in and out of cache memory. The state of each bit in memory is altered as clusters are allocated and deallocated. BITMAP.SYS is updated when the portion of the bitmap in cache is swapped back to disk. Since a portion of the bitmap is always in cache, BITMAP.SYS never reflects the current state of allocated clusters on a disk (unless the disk is dismounted or write-locked).

One of the functions of ANALYZE/DISK_STRUCTURE is to build a current version of BITMAP.SYS from data extracted from INDEXF.SYS, so that BITMAP.SYS accurately reflects the status of free clusters on the disk.

A.3.3 Bad Block File, BADBLK.SYS

The bad block file contains all the bad blocks on the volume. The system detects bad disk blocks dynamically and prevents their reuse once the files to which they are allocated have been deleted.

A.3.4 Master File Directory

The MFD is a file that contains reserved files that control the Files-11 volume directory structure. The MFD lists the known files, in addition to any files or directories that the user enters. The master file directory is itself one of the files (000000.DIR;1) listed in the MFD.

Usually, however, the MFD is used to list the reserved files and users' file directories; users seldom enter files into the MFD, even on private volumes. In fact, on a private volume, it is most convenient for users to create a directory that has the same name as their default directory on a system disk. For an explanation of users' file directories and file specifications, refer to the OpenVMS User's Manual.

When the Backup utility (BACKUP) creates sequential disk save sets, it stores the save-set file in the MFD.

ANALYZE/DISK_STRUCTURE verifies all files contained in the directory structure by making comparisons to INDEXF.SYS. Any file found in INDEXF.SYS that is not traceable through the directory structure is "lost." ANALYZE/DISK_STRUCTURE places lost files in the top-level directory SYSLOST.DIR if you specified /REPAIR in the command.

A.3.5 Core Image File, CORIMG.SYS

The core image file is not used by the operating system.

A.3.6 Volume Set List File, VOLSET.SYS

The volume set list file is used only on relative volume 1 of a volume set. The file contains a list of the labels of all the volumes in the set and the name of the volume set.

ANALYZE/DISK_STRUCTURE uses VOLSET.SYS to locate each volume in the set and confirm the attributes of each volume. Since all volume set information is stored in VOLSET.SYS on relative volume 1, ANALYZE/DISK_STRUCTURE ignores VOLSET.SYS on all other volumes.

A.3.7 Continuation File, CONTIN.SYS

The continuation file is used as the extension file identifier when a file crosses from one volume to another volume of a loosely coupled volume set. This file is used for all but the first volume of a sequential disk save set.

A.3.8 Backup Log File, BACKUP.SYS

The backup log file is reserved for future use.

A.3.9 Pending Bad Block Log File, BADLOG.SYS

The pending bad block log file contains a list of suspected bad blocks on the volume that are not listed in the bad block file.

A.3.10 Quota File, QUOTA.SYS

The quota file is a reserved file that is used by the file system to keep track of the disk usage of each UIC on a volume. If you enable disk quota checking for a volume, the records of the file QUOTA.SYS contain all the UICs on the volume. The system constantly updates QUOTA.SYS to reflect the current disk usage, the maximum allowed disk usage, and the permitted overdraft for each UIC.

During the course of its operations, ANALYZE/DISK_STRUCTURE creates a version of QUOTA.SYS in memory that reflects the actual disk usage for each UIC. This version is eventually compared to the disk version of QUOTA.SYS. If ANALYZE/DISK_STRUCTURE detects any disparities in disk usage, ANALYZE/DISK_STRUCTURE notifies you. If you invoked ANALYZE/DISK_STRUCTURE with the /REPAIR qualifier, the disk version of QUOTA.SYS is updated.

A.3.11 Volume Security Profile, SECURITY.SYS

The volume security profile includes the volume owner UIC, the volume system-owner-group-world (SOGW) protection mask, and the volume access control list (ACL).

A.4 Files--11 ODS Level 1 (VAX Only) Versus Levels 2 and 5

On VAX systems, for reasons of performance, reliability, and security, Files--11 ODS Level 2, a compatible superset of ODS Level 1, is the preferred disk structure on the system. At volume initialization time, Structure Level 2 is the default. (Refer to the INITIALIZE command in the OpenVMS DCL Dictionary.)

On VAX systems, specify ODS Level 1 only for volumes that must be transportable to RSX--11M, RSX--11D, RSX--11M--PLUS, and IAS systems, as these systems support only that structure level. Additionally, you might be required to handle Structure Level 1 volumes transported to OpenVMS from one of these systems.

Where Structure Level 1 volumes are in use on the system, bear in mind the limitations on them that are shown in Table A-4.

Table A-4 Limitations on Files--11 Structure Level 1 Volumes
Disk Only Files--11 ODS--2 disks are protected objects.
Directories No hierarchies of directories and subdirectories, and no ordering of directory entries (that is, the file names) in any way. RSX--11M, RSX--11D, RSX--11M--PLUS, and IAS systems do not support subdirectories and alphabetical directory entries.
Disk quotas Not supported.
Multivolume files and volume sets Not supported.
Placement control Not supported.
Caches No caching of file header blocks, file identification slots, or extent entries.
System disk Cannot be a Structure Level 1 volume.
OpenVMS Cluster access Local access only; cannot be shared across a cluster.
Clustered allocation Not supported.
Backup home block Not supported.
Protection code E E means "extend" for the RSX--11M operating system but is ignored by OpenVMS.
File versions Limited to 32,767; version limits are not supported.
Enhanced protection features (for example, access control lists) Not supported.
Long file names Not supported.
RMS journaling Not supported.
RMS execution statistics monitoring Not supported.

Future enhancements to OpenVMS software will be based primarily on Structure Level 5; therefore, Structure Level 1 volumes might be further restricted in the future.

Appendix B
Tables of Time Differential Factors

The tables in this appendix show the time differential factors (TDFs) of various locations in the world. Each table contains a list of locations in a specific region. The information in the tables is believed to be accurate at the time of publication.


Time zone rules are under control of each country, and are subject to change for political and other reasons. For up-to-date information, see the following web locations:


Table B-1 lists the time differential factors for Europe.

Table B-1 TDFs for Europe
Region Standard
Time TDF
Daylight Saving
Time TDF
Great Britain, Ireland 0:00 +1:00
Western European Time 0:00 +1:00
Iceland 0:00 ---
Middle European Time +1:00 +2:00
Poland +2:00 +3:00
Eastern European Time +2:00 +3:00
Turkey +2:00 +3:00

Table B-2 lists the time differential factors for North America.

Table B-2 TDFs for North America
Region Standard
Time TDF
Daylight Saving
Time TDF
U.S./Eastern Time -5:00 -4:00
U.S./Central Time -6:00 -5:00
U.S./Mountain Time -7:00 -6:00
U.S./Pacific Time -8:00 -7:00
U.S./Indiana (East) -5:00 ---
U.S./Alaska -9:00 -8:00
U.S./Arizona -7:00 ---
U.S./Navajo -7:00 -6:00
U.S./Michigan -5:00 -4:00
U.S./Aleutian Islands -10:00 -9:00
U.S./Hawaii -10:00 ---
U.S./Samoa -11:00 ---
Canada/Newfoundland -3:30 -2:30
Canada/Atlantic -4:00 -3:00
Canada/Eastern -5:00 -4:00
Canada/Central -6:00 -5:00
Canada/East--Saskatchewan -6:00 ---
Canada/Mountain -7:00 -6:00
Canada/Pacific -8:00 -7:00
Canada/Yukon -9:00 -8:00

Table B-3 lists the time differential factors for Central and South America.

Table B-3 TDFs for Central and South America
Region Standard
Time TDF
Daylight Saving
Time TDF
Mexico/BajaNorte -8:00 -7:00
Mexico/BajaSur -7:00 ---
Mexico/General -6:00 ---
Cuba -5:00 -4:00
Jamaica -5:00 -4:00
Brazil/East -3:00 -2:00
Brazil/West -4:00 -3:00
Brazil/Acre -5:00 -4:00
Brazil/DeNoronha -2:00 -1:00
Chile/Regional -4:00 -3:00
Chile/Easter Island -6:00 -5:00

Table B-4 lists the time differential factors for Asia.

Table B-4 TDFs for Asia
Region Standard
Time TDF
Daylight Saving
Time TDF
PRC (Mainland China) +8:00 +9:00
ROK (Korea) +9:00 +10:00
Israel +2:00 +3:00
Iran +3:30 +4:30
Japan +9:00 ---
Singapore +8:00 ---
Hong Kong +8:00 ---
ROC (Taiwan) +8:00 ---

Table B-5 lists the time differential factors for the South Pacific.

Table B-5 TDFs for the South Pacific
Region Standard
Time TDF
Daylight Saving
Time TDF
Australia/Tasmania +10:00 +11:00
Australia/Queensland (standard time only) +10:00 ---
Australia/Queensland +10:00 +11:00
Australia/North +9:30 ---
Australia/West +8:00 ---
Australia/South +9:30 +10:30
Australia/Victoria +10:00 +11:00
Australia/New South Wales +10:00 +11:00
New Zealand +12:00 +13:00

Table B-6 lists the time differential factors for Antarctica.

Table B-6 TDFs for Antarctica
Region Standard
Time TDF
Daylight Saving
Time TDF
Antarctica +0:00 ---

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