File - Revision history

Jane.doe at 08:45, 6 July 2023

2023-07-06T08:45:23Z

← Older revision		Revision as of 08:45, 6 July 2023
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	* [[Indexed File\|indexed]]		* [[Indexed File\|indexed]]

	To find out the organization of a particular file, do a DIRECTORY/FULL.		To find out the organization of a particular file, do a [[DIRECTORY (command) \|DIRECTORY]]/FULL.

	Record Access Mode		Record Access Mode

Jane.doe: /* Directory Files */

2019-12-15T04:58:04Z

Directory Files

← Older revision		Revision as of 04:58, 15 December 2019
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	=Directory Files=		=Directory Files=
	Directory files are special files that contain the list of files in a directory and their FIDs. Directory files always have the extension of .DIR and version 1.		[[Directory file\|Directory files]] are special files that contain the list of files in a directory and their FIDs. Directory files always have the extension of .DIR and version 1 (files with version numbers greater than one cannot be used as directory files). With sufficient privileges, the directory label can be removed from a file with [[SET FILE]]/NODIRECTORY. You can see if a file is a directory file with [[DIRECTORY]]/FULL; running [[F$FILE_ATTRIBUTES()\|F$FILE_ATTRIBUTES]](filespec,"DIRECTORY") on a file returns "TRUE" if it is a directory file.

	=Metadata=		=Metadata=

Jane.doe: /* FID */

2019-12-15T04:54:10Z

FID

← Older revision		Revision as of 04:54, 15 December 2019
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	=FID=		=FID=
	A file is idenitified by the [[File_ID\|file ID]] which consists of three numbers:		A file is idenitified by the [[File_ID\|file ID]] (for example, "277058,4,0") which consists of three numbers:
	* the file number - the offset into [[INDEXF.SYS]] where the [[File header\|file header]] is stored		* the file number - the offset into [[INDEXF.SYS]] where the [[File header\|file header]] is stored
	* the file sequence number specifying how many times this file number has been used		* the file sequence number specifying how many times this file number has been used

Jane.doe: /* File Organization */

2019-12-15T00:21:41Z

File Organization

← Older revision		Revision as of 00:21, 15 December 2019
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	[[RMS]] supports the following file organization types:		[[RMS]] supports the following file organization types:

	* sequential		* [[Sequential File\|sequential]]
	* relative		* [[Relative File\|relative]]
	* indexed		* [[Indexed File\|indexed]]

	To find out the organization of a particular file, do a DIRECTORY/FULL.		To find out the organization of a particular file, do a DIRECTORY/FULL.

	~~==Sequential File Organization==~~
	In sequential file organization, records are arranges one after the other in the order in which they are stored. When editing a sequential file, new records cannot be inserted between existing records because no physical space separates them - you can only add records to the end of the file.

	~~Sequential file organization is supported for all device types; this is the only file organization for non-disk devices. A sequential file is created by default when you use the CREATE command.~~

	~~==Relative File Organization==~~
	The relative file organization allows sequential and random access of records. A relative file consists of a series of numbered fixed-length records; RMS uses the relative record number - the record's position relative to the beginning of the file - to randomly access records. Relative files allow random get and put operations and can be write-shared.

	~~==Indexed File Organization==~~
	~~Indexed files store data records in an index structure ordered by the primary key; data can be retrieved using index structures ordered by primary or alternate keys.~~

	Record Access Mode		Record Access Mode

Tonvanderzwet at 17:54, 26 October 2019

2019-10-26T17:54:20Z

← Older revision		Revision as of 17:54, 26 October 2019
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	</nowiki>		</nowiki>

	=See also==		=See also=
	* {{Template:Fap}}		* {{Template:Fap}}

Tonvanderzwet at 12:14, 26 October 2019

2019-10-26T12:14:42Z

← Older revision		Revision as of 12:14, 26 October 2019
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	=FID=		=FID=
	A file is idenitified by the [[File_ID\|file ID]] which consists of three numbers:		A file is idenitified by the [[File_ID\|file ID]] which consists of three numbers:
	* the file number - the offset into [[INDEXF.SYS]] where the [[File ~~Header~~\|file header]] is stored		* the file number - the offset into [[INDEXF.SYS]] where the [[File header\|file header]] is stored
	* the file sequence number specifying how many times this file number has been used		* the file sequence number specifying how many times this file number has been used
	* the relative volume number specifying the number of the volume in the [[Volume Set\|volume set]] where the file is stored		* the relative volume number specifying the number of the volume in the [[Volume Set\|volume set]] where the file is stored

Tonvanderzwet at 12:13, 26 October 2019

2019-10-26T12:13:29Z

← Older revision		Revision as of 12:13, 26 October 2019
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	A '''file''' is a data structure for storing information on a storage media, an ordered collection of logically related records treated as a unit. File operations are provided by the [[RMS\|Record Management Services]]. Files are identified by [[File ID\|file IDs]] which contain the location of the [[File ~~Header~~\|file header]]. File headers stored in [[INDEXF.SYS]] contain file metadata and pointers to where the file data is stored on disk.		A '''file''' is a data structure for storing information on a storage media, an ordered collection of logically related records treated as a unit. File operations are provided by the [[RMS\|Record Management Services]]. Files are identified by [[File ID\|file IDs]] which contain the location of the [[File header\|file header]]. File headers stored in [[INDEXF.SYS]] contain file metadata and pointers to where the file data is stored on disk.

	=File Organization=		=File Organization=

Tonvanderzwet at 12:12, 26 October 2019

2019-10-26T12:12:48Z

← Older revision		Revision as of 12:12, 26 October 2019
Line 1:		Line 1:
	A '''file''' is a data structure for storing information on a storage media, an ordered collection of logically related records treated as a unit. File operations are provided by the [[RMS\|Record Management Services]]. Files are identified by [[~~FID~~\|file IDs]] which contain the location of the [[File Header\|file header]]. File headers stored in [[INDEXF.SYS]] contain file metadata and pointers to where the file data is stored on disk.		A '''file''' is a data structure for storing information on a storage media, an ordered collection of logically related records treated as a unit. File operations are provided by the [[RMS\|Record Management Services]]. Files are identified by [[File ID\|file IDs]] which contain the location of the [[File Header\|file header]]. File headers stored in [[INDEXF.SYS]] contain file metadata and pointers to where the file data is stored on disk.

	=File Organization=		=File Organization=

Darya.zelenina: corrected the File_ID link

2019-04-05T09:23:43Z

corrected the File_ID link

← Older revision		Revision as of 09:23, 5 April 2019
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	=FID=		=FID=
	A file is idenitified by the [[~~FID~~\|file ID]] which consists of three numbers:		A file is idenitified by the [[File_ID\|file ID]] which consists of three numbers:
	* the file number - the offset into [[INDEXF.SYS]] where the [[File Header\|file header]] is stored		* the file number - the offset into [[INDEXF.SYS]] where the [[File Header\|file header]] is stored
	* the file sequence number specifying how many times this file number has been used		* the file sequence number specifying how many times this file number has been used
Line 65:		Line 65:

	=Aliases=		=Aliases=
	Several directory entries with different names possibly found in different directories can point to the same [[~~FID~~]] and thus same data on disk. This is called aliases or links.		Several directory entries with different names possibly found in different directories can point to the same [[File_ID]] and thus same data on disk. This is called aliases or links.

	In the following example, an alias is created for REPORT.DAT:		In the following example, an alias is created for REPORT.DAT:

Darya.zelenina: Created page with "A '''file''' is a data structure for storing information on a storage media, an ordered collection of logically related records treated as a unit. File operations are provided..."

2019-03-30T18:20:03Z

Created page with "A '''file''' is a data structure for storing information on a storage media, an ordered collection of logically related records treated as a unit. File operations are provided..."

New page

A '''file''' is a data structure for storing information on a storage media, an ordered collection of logically related records treated as a unit. File operations are provided by the [[RMS|Record Management Services]]. Files are identified by [[FID|file IDs]] which contain the location of the [[File Header|file header]]. File headers stored in [[INDEXF.SYS]] contain file metadata and pointers to where the file data is stored on disk.

=File Organization=
[[RMS]] supports the following file organization types:

* sequential
* relative
* indexed

To find out the organization of a particular file, do a DIRECTORY/FULL.

==Sequential File Organization==
In sequential file organization, records are arranges one after the other in the order in which they are stored. When editing a sequential file, new records cannot be inserted between existing records because no physical space separates them - you can only add records to the end of the file.

Sequential file organization is supported for all device types; this is the only file organization for non-disk devices. A sequential file is created by default when you use the CREATE command.

==Relative File Organization==
The relative file organization allows sequential and random access of records. A relative file consists of a series of numbered fixed-length records; RMS uses the relative record number - the record's position relative to the beginning of the file - to randomly access records. Relative files allow random get and put operations and can be write-shared.

==Indexed File Organization==
Indexed files store data records in an index structure ordered by the primary key; data can be retrieved using index structures ordered by primary or alternate keys.

Record Access Mode
RMS provides two record access modes: [[Sequential Access to Files|sequential access]] and [[Random Access to Files|random access]].
Random access can be further catalogued as one of the three following modes:
* Random access by key value
* Random access by relative record number
* Random access by record file address (RFA)
Although you cannot change its file organization after you create a file, you can change the record access mode each time you access a record in the file. For example, a relative file can be processed in sequential access mode one time and in a random access mode the next time.

{| class="wikitable"
! rowspan="2;" | Access Mode
! colspan="3;" | File Organization
|-
! colspan='col' | Sequential
! colspan='col' | Relative
! colspan='col' | Indexed
|-
| Sequential
| Yes
| Yes
| Yes
|-
| Random by relative record number
| Permitted with fixed-length record format on disk devices only
| Yes
| No
|-
| Random by key value
| No
| No
| Yes
|-
| Random by record file address
| Permitted on disk devices only
| Yes
| No
|}

=FID=
A file is idenitified by the [[FID|file ID]] which consists of three numbers:
* the file number - the offset into [[INDEXF.SYS]] where the [[File Header|file header]] is stored
* the file sequence number specifying how many times this file number has been used
* the relative volume number specifying the number of the volume in the [[Volume Set|volume set]] where the file is stored

=Aliases=
Several directory entries with different names possibly found in different directories can point to the same [[FID]] and thus same data on disk. This is called aliases or links.

In the following example, an alias is created for REPORT.DAT:

<nowiki>
$ dir

Directory DKA0:[JDOE]

DATA.DIR;1 REPORT.DAT;1

Total of 2 files.
$ set file/enter=report_alias.dat
_File: report.dat
$ dir

Directory DKA0:[JDOE]

DATA.DIR;1 REPORT.DAT;1 REPORT_ALIAS.DAT;1

Total of 3 files.
$ dir /file_id

Directory DKA0:[JDOE]

DATA.DIR;1 (6170,17222,0)
REPORT.DAT;1 (6169,17222,0)
REPORT_ALIAS.DAT;1 (6169,17222,0)

Total of 3 files.

</nowiki>

Normally when a file that has an alias is deleted, a dangling directory entry appears - that is, the alias cannot be used to access the file header and the file is "lost":

<nowiki>
$ delete report.dat;1
$ type REPORT_ALIAS.DAT;1
%TYPE-W-OPENIN, error opening DKA0:[JDOE]REPORT_ALIAS.DAT;1 as input
-RMS-E-FNF, file not found
</nowiki>

[[ODS-5]] volumes with [[Hardlink|hardlinks]] enabled support hard links: that is, aliases that can act like files. On a volume with hard links enabled, you can delete the original file, and if there is at least one alias pointing to the file header, the file data is accessible.

=Directory Files=
Directory files are special files that contain the list of files in a directory and their FIDs. Directory files always have the extension of .DIR and version 1.

=Metadata=
File metadata are stored in the file header in [[INDEXF.SYS]]. You can view it with DIRECTORY/FULL or DUMP/HEADER:

<nowiki>
$ dir/full data.dir

Directory DKA0:[JDOE]

DATA.DIR;1 File ID: (6170,17222,0)
Size: 1/16 Owner: [JDOE]
Created: 29-MAR-2019 15:56:38.74
Modified: 29-MAR-2019 15:56:38.74 (0)
Expires: <None specified>
Backup: <No backup recorded>
Effective: <None specified>
Recording: <None specified>
Accessed: <None specified>
Attr Mod: <None specified>
Data Mod: <None specified>
Linkcount: 1
File organization: Sequential
Shelved state: Online
Caching attribute: Writethrough
File attributes: Allocation: 16, Extend: 0, Global buffer count: 0
No default version limit, Contiguous, MoveFile disabled
Directory file
Record format: Variable length, maximum 512 bytes, longest 512 bytes
Record attributes: No carriage control, Non-spanned
RMS attributes: None
Journaling enabled: None
File protection: System:RWE, Owner:RWE, Group:RE, World:E
Access Cntrl List: None
Client attributes: None

Total of 1 file, 1/16 blocks.
</nowiki>

=See also==
* {{Template:Fap}}