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HP OpenVMS System Manager's Manual, Volume 2:... |
Files-11 Disk Structure |
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This section also points out the files ANALYZE/DISK_STRUCTURE uses. ANALYZE/DISK_STRUCTURE makes an in-memory copy of what these files should look like and compares it with the current version. The utility reports and repairs (if you specify the /REPAIR qualifier) any discrepancies found during these comparisons.
Reserved Files shows the reserved files used by Files--11 Levels 1, 2, and 5, and files used by ANALYZE/DISK_STRUCTURE.
| Reserved File | File Name | Structure Level 11 | Structure Levels 2 and 5 | ANALYZE/ DISK_STRUCTURE |
|---|---|---|---|---|
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Index file
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INDEXF.SYS;1
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X
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X
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X
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Storage bitmap
file
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BITMAP.SYS;1
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X
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X
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X
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Bad block file
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BADBLK.SYS;1
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X
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X
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Master file directory
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000000.DIR;1
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X
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X
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X
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Core image
file
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CORIMG.SYS;1
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X
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X
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Volume set
list file
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VOLSET.SYS;1
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X
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X
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Continuation
file
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CONTIN.SYS;1
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X
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Backup log
file
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BACKUP.SYS;1
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X
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Pending bad
block
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BADLOG.SYS;1
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X
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Quota file
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QUOTA.SYS
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X
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Volume security profile
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SECURITY.SYS
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X
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Index File,
INDEXF.SYS
Every Files--11 volume
has an index file, which is created when the volume is initialized.
(You cannot use a disk as a Files-11 disk until it has been initialized
with the INITIALIZE command.)
INDEXF.SYS is a large, extendable file made up of several sections. These sections provide the operating system with the information necessary to identify a Files-11 volume, initially access that volume, and locate all the files on that volume (including INDEXF.SYS itself).
Contents of Files--11 Index File shows the information that is in INDEXF.SYS. After the table are additional explanations of boot block, home block, and file headers.
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 the Process Control chapter in the HP OpenVMS System Manager's Manual, Volume 1: Essentials.
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:
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.
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 Areas of Data in File Headers.
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.
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.
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.
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.
Core Image File, CORIMG.SYS
The core image file
is not used by the operating system.
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.
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.
Backup Log File, BACKUP.SYS
The backup log file
is reserved for future use.
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.
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.
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).
1 VAX specific.
( Number takes you back )
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