File architecture overview - Revision history

ELowell at 16:54, 12 May 2014

2014-05-12T16:54:21Z

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	[[Table A (File architecture)\|Table A]] contains three structures: a file dictionary, a set of <var>MANY-VALUED</var> pages, and a set of <var>FEW-VALUED</var> pages.		[[Table A (File architecture)\|Table A]] contains three structures: a file dictionary, a set of <var>MANY-VALUED</var> pages, and a set of <var>FEW-VALUED</var> pages.

	The file dictionary contains the file's field group and field names and their attributes. Some field attributes (notably <var>[[Field design ~~(File management)~~#CODED and NON-CODED attributes\|CODED]]</var>) require lists of values to be maintained. These lists are stored either in the [[Field design ~~(File management)~~#FEW-VALUED and MANY-VALUED attributes\|FEW-VALUED or MANY-VALUED]] structures.		The file dictionary contains the file's field group and field names and their attributes. Some field attributes (notably <var>[[Field design#CODED and NON-CODED attributes\|CODED]]</var>) require lists of values to be maintained. These lists are stored either in the [[Field design#FEW-VALUED and MANY-VALUED attributes\|FEW-VALUED or MANY-VALUED]] structures.

	Table A usually is small in relation to the rest of the file. The field name section in particular should be as small as possible to aid efficient access, especially if your site uses field name variables		Table A usually is small in relation to the rest of the file. The field name section in particular should be as small as possible to aid efficient access, especially if your site uses field name variables
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	pairs in a record is in the tens of millions.</p>		pairs in a record is in the tens of millions.</p>
	<p>		<p>
	There is only a limited fixed format for a record ([[Field design ~~(File management)~~#Preallocated fields (OCCURS attribute)\|preallocated fields]]). Almost any number of fields		There is only a limited fixed format for a record ([[Field design#Preallocated fields (OCCURS attribute)\|preallocated fields]]). Almost any number of fields
	can appear almost any number of times in almost any order.		can appear almost any number of times in almost any order.
	Each record is automatically assigned a unique internal record		Each record is automatically assigned a unique internal record
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	<tr><td>Hashed Index		<tr><td>Hashed Index
	<td>Consists of Table C, which indexes <var>[[Field design ~~(File management)~~#KEY and NON-KEY attributes\|KEY]]</var> and <var>[[Field design ~~(File management)~~#NUMERIC RANGE and NON-RANGE attributes\|NUMERIC RANGE]]</var> values in fields, along with either a single direct pointer (per segment) to a base record in Table B or to a secondary index (of list or bitmap pages) located in Table D.</td></tr>		<td>Consists of Table C, which indexes <var>[[Field design#KEY and NON-KEY attributes\|KEY]]</var> and <var>[[Field design#NUMERIC RANGE and NON-RANGE attributes\|NUMERIC RANGE]]</var> values in fields, along with either a single direct pointer (per segment) to a base record in Table B or to a secondary index (of list or bitmap pages) located in Table D.</td></tr>
	</table>		</table>

Dme at 14:42, 10 May 2014

2014-05-10T14:42:11Z

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	<p>Internally, these pages are organized into tables: the [[File Control Table (File architecture)\|File Control Table]] (FCT), [[Table A (File architecture)\|Table A]], [[Table B (File architecture)\|Table B]], [[Table C (File architecture)\|Table C]], [[Table D (File architecture)\|Table D]], [[Table E (File architecture)\|Table E]], and [[Table X (File architecture)\|Table X]]. Any pages in the file not allocated to one of these tables are considered free space. See [[Managing file and table sizes]] for how this free space can be applied to the other tables.</p>		<p>Internally, these pages are organized into tables: the [[File Control Table (File architecture)\|File Control Table]] (FCT), [[Table A (File architecture)\|Table A]], [[Table B (File architecture)\|Table B]], [[Table C (File architecture)\|Table C]], [[Table D (File architecture)\|Table D]], [[Table E (File architecture)\|Table E]], and [[Table X (File architecture)\|Table X]]. Any pages in the file not allocated to one of these tables are considered free space. See [[Managing file and table sizes]] for how this free space can be applied to the other tables.</p>

			<div id="fileComponents"></div>
	==The components of a Model 204 file==		==The components of a Model 204 file==

Dme: /* Procedures and miscellaneous structures */

2014-05-10T04:09:50Z

Procedures and miscellaneous structures

← Older revision		Revision as of 04:09, 10 May 2014
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	Table D also contains a map of the preallocated fields (used whenever a new record is stored). Use the <var>[[DISPLAY RECORD command\|DISPLAY RECORD]]</var> command to view this map.		Table D also contains a map of the preallocated fields (used whenever a new record is stored). Use the <var>[[DISPLAY RECORD command\|DISPLAY RECORD]]</var> command to view this map.


	~~[[Category:File architecture and management]]~~
	[[Category:File architecture]]		[[Category:File architecture]]

JAL at 21:22, 17 April 2014

2014-04-17T21:22:06Z

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	pairs in a record is in the tens of millions.</p>		pairs in a record is in the tens of millions.</p>
	<p>		<p>
	There is only a limited fixed format for a record ([[Field design (File management)#Preallocated fields ~~(OCCURS attribute)~~ (OCCURS attribute)\|preallocated fields]]). Almost any number of fields		There is only a limited fixed format for a record ([[Field design (File management)#Preallocated fields (OCCURS attribute)\|preallocated fields]]). Almost any number of fields
	can appear almost any number of times in almost any order.		can appear almost any number of times in almost any order.
	Each record is automatically assigned a unique internal record		Each record is automatically assigned a unique internal record

JALWiccan: Automatically generated page update

2014-04-17T20:58:32Z

Automatically generated page update

← Older revision		Revision as of 20:58, 17 April 2014
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	pairs in a record is in the tens of millions.</p>		pairs in a record is in the tens of millions.</p>
	<p>		<p>
	There is only a limited fixed format for a record ([[Field design (File management)#Preallocated fields (OCCURS attribute)\|preallocated fields]]). Almost any number of fields		There is only a limited fixed format for a record ([[Field design (File management)#Preallocated fields (OCCURS attribute) (OCCURS attribute)\|preallocated fields]]). Almost any number of fields
	can appear almost any number of times in almost any order.		can appear almost any number of times in almost any order.
	Each record is automatically assigned a unique internal record		Each record is automatically assigned a unique internal record

JALWiccan: Automatically generated page update

2014-04-17T20:51:56Z

Automatically generated page update

← Older revision		Revision as of 20:51, 17 April 2014
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	Model 204 records are best thought of as very loosely defined containers, with almost no fixed structure.		Model 204 records are best thought of as very loosely defined containers, with almost no fixed structure.

	The fundamental elements of Model ~~204’s~~ logical data structure are:		The fundamental elements of Model 204’s logical data structure are:
	<table style="width:80%">		<table style="width:80%">
	<tr><td>Record</td>		<tr><td>Record</td>
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	pairs in a record is in the tens of millions.</p>		pairs in a record is in the tens of millions.</p>
	<p>		<p>
	There is only a limited fixed format for a record ([[Field design (File management)#Preallocated fields\|preallocated fields]]). Almost any number of fields		There is only a limited fixed format for a record ([[Field design (File management)#Preallocated fields (OCCURS attribute)\|preallocated fields]]). Almost any number of fields
	can appear almost any number of times in almost any order.		can appear almost any number of times in almost any order.
	Each record is automatically assigned a unique internal record		Each record is automatically assigned a unique internal record

JAL at 01:02, 24 January 2014

2014-01-24T01:02:45Z

Show changes

ELowell at 22:44, 18 December 2013

2013-12-18T22:44:03Z

← Older revision		Revision as of 22:44, 18 December 2013
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	[[Table B (File architecture)\|Table B]] contains (at least) the base data of all the records in the file. These base records contain pointers to any extensions which exist (whether they are elsewhere in Table B or in Table X).		[[Table B (File architecture)\|Table B]] contains (at least) the base data of all the records in the file. These base records contain pointers to any extensions which exist (whether they are elsewhere in Table B or in Table X).

	[[Table X (File ~~Architecture~~)\|Table X]] when enabled, holds all extension records. Table B is then used		[[Table X (File architecture)\|Table X]] when enabled, holds all extension records. Table B is then used
	to store only base records, thus, maximizing the possible number of records can be stored regardless of the number of		to store only base records, thus, maximizing the possible number of records can be stored regardless of the number of
	extension records.		extension records.

Admin at 22:31, 18 December 2013

2013-12-18T22:31:53Z

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	extension records.		extension records.

	[[Table E (File ~~Architecture~~)\|Table E]] (when enabled) contains Large Object data for the file. The pointer to the starting point of the LOB is contained in Table B or X.		[[Table E (File architecture)\|Table E]] (when enabled) contains Large Object data for the file. The pointer to the starting point of the LOB is contained in Table B or X.

Admin at 22:29, 18 December 2013

2013-12-18T22:29:45Z

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	\|-		\|-
	! scope="row"\| Ordered Index		! scope="row"\| Ordered Index
	\| Is composed of the Ordered Index B-tree, contained in Table D, for [[~~Table_D_~~(~~File_Architecture~~)#Ordered_Index\|ORDERED]] fields along with either a number of IMMEDiate pointers to the record in Table B, or to a secondary index (of list or bitmap pages) located in Table D.		\| Is composed of the Ordered Index B-tree, contained in Table D, for [[Table D (File architecture)#Ordered_Index\|ORDERED]] fields along with either a number of IMMEDiate pointers to the record in Table B, or to a secondary index (of list or bitmap pages) located in Table D.

	\|-		\|-