Page (File architecture): Difference between revisions
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(Created page with "A page is the underlying structure of the data-set(s) that comprise a Model 204 file. All pages are 6184 bytes. When a file is created,...") |
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A page is the underlying structure | A page is the underlying structure applied to the data-set(s) that comprise a Model 204 file. | ||
All pages are 6184 bytes. | All pages are 6184 bytes. | ||
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When a file is [[Creating a File (File Management)|created]], the pages in the file are formatted into: | When a file is [[Creating a File (File Management)|created]], the pages in the file are formatted into: | ||
* 6144 bytes of 'usable' space (how | * 6144 bytes of 'usable' space (how the space is used depends on the page type) | ||
* a 40 byte page trailer | * a 40 byte page trailer | ||
== The page Trailer == | |||
The page trailer contains: | |||
* the file name. This is the name used in the [[CREATE command: File|Create]] process | |||
* the date / time when the page was last [[INITIALIZE command|initialized]]. | |||
* the date / time the page was last written to the file | |||
* data used in the [[CHECKPOINT command|checkpoint]] process | |||
* the table that this page is part of (a numeric representation (see note 1)) | |||
* the sequential page number within the table | |||
Note 1: FCT = 0, Table A = 1, Table B = 2, Table C = 3, Table D = 4, Table E = 5 and Table X = 6. Because of INCREASE and DECREASE commands after the initial CREATE, the pages for a table may not be contiguous. | |||
[[Category:File Architecture and Management]] | [[Category:File Architecture and Management]] | ||
[[Category:File Architecture]] | [[Category:File Architecture]] | ||
Revision as of 00:27, 4 April 2013
A page is the underlying structure applied to the data-set(s) that comprise a Model 204 file.
All pages are 6184 bytes.
When a file is created, the pages in the file are formatted into:
- 6144 bytes of 'usable' space (how the space is used depends on the page type)
- a 40 byte page trailer
The page Trailer
The page trailer contains:
- the file name. This is the name used in the Create process
- the date / time when the page was last initialized.
- the date / time the page was last written to the file
- data used in the checkpoint process
- the table that this page is part of (a numeric representation (see note 1))
- the sequential page number within the table
Note 1: FCT = 0, Table A = 1, Table B = 2, Table C = 3, Table D = 4, Table E = 5 and Table X = 6. Because of INCREASE and DECREASE commands after the initial CREATE, the pages for a table may not be contiguous.