Page (File architecture): Difference between revisions
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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 the space is used depends on the page | * 6144 bytes of 'usable' space (how the space is used depends on the table where the page resides) | ||
* a 40 byte page trailer | * a 40 byte page trailer | ||
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Note 1: FCT = | Note 1: FCT = 00, Table A = 01, Table B = 02, Table C = 03, Table D = 04, Table E = 40 and Table X = 20. Because of INCREASE and DECREASE commands after the initial CREATE, the pages for a table may not be contiguous. | ||
[[Category:File architecture]] | [[Category:File architecture]] | ||
Revision as of 11:40, 16 May 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 table where the page resides)
- 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 = 00, Table A = 01, Table B = 02, Table C = 03, Table D = 04, Table E = 40 and Table X = 20. Because of INCREASE and DECREASE commands after the initial CREATE, the pages for a table may not be contiguous.