File size calculation in detail - Revision history

Goff: /* Computing the file size multiplier (N) */

2024-06-11T22:06:18Z

Computing the file size multiplier (N)

← Older revision		Revision as of 22:06, 11 June 2024
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	===Computing the file size multiplier (N)===		===Computing the file size multiplier (N)===
	<p>		<p>
	To minimize disk storage space and to optimize record retrieval techniques, the records in Table B are divided into internal file segments that are transparent to the user. The maximum number of records stored in one file segment is 49,152 (that is, eight times a page size of ~~6184~~). </p>		To minimize disk storage space and to optimize record retrieval techniques, the records in Table B are divided into internal file segments that are transparent to the user. The maximum number of records stored in one file segment is 49,152 (that is, eight times a page size of 6144). </p>
	<p>		<p>
	Both Table C and Table D space estimation formulas depend upon the file size multiplier <var>N</var>, which represents the number of internal file segments. Use the following equation to calculate <var>N</var>:</p>		Both Table C and Table D space estimation formulas depend upon the file size multiplier <var>N</var>, which represents the number of internal file segments. Use the following equation to calculate <var>N</var>:</p>
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	<p>		<p>
	For space estimation purposes, the records are considered to be distributed evenly among the segments. If the records are not distributed evenly, make separate estimates for each segment individually.</p>		For space estimation purposes, the records are considered to be distributed evenly among the segments. If the records are not distributed evenly, make separate estimates for each segment individually.</p>

	==Sizing Table C==		==Sizing Table C==

JAL: /* Estimating Ordered Index space (OI) for each ORDERED field */ add link

2018-04-23T20:22:33Z

Estimating Ordered Index space (OI) for each ORDERED field: add link

← Older revision		Revision as of 20:22, 23 April 2018
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	=====Estimating Ordered Index space (OI) for each ORDERED field=====		=====Estimating Ordered Index space (OI) for each ORDERED field=====
	<p>		<p>
	For each field in the file that has the ORDERED attribute, the number of Table D pages required for the section of the Ordered Index B-tree structure that indexes the field is estimated as follows. </p>		For each field in the file that has the <var>ORDERED</var> attribute, the number of Table D pages required for the section of the Ordered Index B-tree structure that indexes the field is estimated as follows. </p>
	<ol>		<ol>
	<li>Estimate the following numbers:		<li>Estimate the following numbers:
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	<li>Estimate the average length (<code>AV</code>).		<li>Estimate the average length (<code>AV</code>).
	<p>		<p>
	First estimate the average length of the distinct values stored in the ORDERED field. For numeric values of ORDERED NUMERIC fields, the average length of the numeric values is 8. Compute the following:</p>		First estimate the average length of the distinct values stored in the <var>ORDERED</var> field. For numeric values of <var>ORDERED NUMERIC</var> fields, the average length of the numeric values is 8. Compute the following:</p>
	<p class="code">AV = estimated av. length of ORDERED values + 1		<p class="code">AV = estimated av. length of ORDERED values + 1
	</p></li>		</p></li>

	<li>Divide the ORDERED values into categories. To estimate space for the Ordered Index, perform separate calculations on each of the following categories of distinct field value:		<li>Divide the <var>ORDERED</var> values into categories. To estimate space for the Ordered Index, perform separate calculations on each of the following categories of distinct field value:
	<table>		<table>
	<tr class="head">		<tr class="head">
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	<td>		<td>
	<p>		<p>
	A greater number of records per segment than the setting of the field's IMMED parameter. </p>		A greater number of records per segment than the setting of the field's <var>IMMED</var> parameter. </p>
	<p>		<p>
	ValC = the number of values in category C</p>		ValC = the number of values in category C</p>
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	For the values in category B, first estimate the average number of records per segment that has one of the values in category B. </p>		For the values in category B, first estimate the average number of records per segment that has one of the values in category B. </p>
	<p>		<p>
	Let <var>AB</var> represent the average number of records per segment with one of the values in category B. <var>AB</var> is between 1 and the value of the IMMED parameter for that field.</p>		Let <var>AB</var> represent the average number of records per segment with one of the values in category B. <var>AB</var> is between 1 and the value of the <var>IMMED</var> parameter for that field.</p>
	<p>		<p>
	The total length of the Ordered Index entries placed in category B is:</p>		The total length of the Ordered Index entries placed in category B is:</p>
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	If the values are not evenly distributed, estimate ENa, ENb, and ENc (as appropriate) for each segment in which the values occur.</p>		If the values are not evenly distributed, estimate ENa, ENb, and ENc (as appropriate) for each segment in which the values occur.</p>
	<p class="note"><b>Note:</b>		<p class="note"><b>Note:</b>
	The value calculated as OIB should roughly correspond to the value of the OINBYTES parameter after the file is fully loaded. OINBYTES is a file table parameter that displays the current number of Ordered Index B-tree entry bytes. </p></li>		The value calculated as OIB should roughly correspond to the value of the <var>[[OINBYTES parameter\|OINBYTES]]</var> parameter after the file is fully loaded. <var>OINBYTES</var> is a file table parameter that displays the current number of Ordered Index B-tree entry bytes. </p></li>
	</ol>		</ol>

ELowell: /* z/VM example */

2017-04-14T23:20:05Z

z/VM example

← Older revision		Revision as of 23:20, 14 April 2017
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	<p>		<p>
	The minidisk where the allocation is to be performed must be accessed before issuing M204UTIL ALLOCATE from z/VM. M204UTIL ALLOCATE does not catalog data sets.		The minidisk where the allocation is to be performed must be accessed before issuing M204UTIL ALLOCATE from z/VM. M204UTIL ALLOCATE does not catalog data sets.
	For further description of M204UTIL see the ~~<var class="book">Rocket Model 204 System Manager's Guide</var>~~.</p>		For further description of M204UTIL, see [[Defining the runtime environment (CCAIN)]].</p>

	====ALLOCATE control statement====		====ALLOCATE control statement====
	<p>		<p>

ELowell: /* Overview */

2015-04-13T21:13:21Z

Overview

← Older revision		Revision as of 21:13, 13 April 2015
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	<p>		<p>
	Rocket Software recommends a more flexible, ad-hoc approach, as discussed in [[File ~~size calculation~~]].</p>		Rocket Software recommends a more flexible, ad-hoc approach, as discussed in [[File sizing introduction]].</p>
	<p>		<p>
	What follows is detail which is unlikely ever to be done more than once by a file manager. That said, the detail provided is useful and may be referred to to help in the ad-hoc design approach.</p>		What follows is detail which is unlikely ever to be done more than once by a file manager. That said, the detail provided is useful and may be referred to to help in the ad-hoc design approach.</p>

	==The detailed design process==		==The detailed design process==
	<p>		<p>

JAL: add link

2015-03-02T20:29:58Z

add link

← Older revision		Revision as of 20:29, 2 March 2015
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	The multiplier of 1.1 in the ATRPG formula allows room for adding field names that were not originally part of the file, as well as for redefining field names. When the REDEFINE command is used, one or two bytes can be added to or deleted from a Table A entry, if the LEVEL or UPDATE option is changed. The amount of overhead required for a redefined field is computed according to the rules for the original definition (see ASTRPPG above). When you delete a field definition, all but two bytes are made available for reuse. </p>		The multiplier of 1.1 in the ATRPG formula allows room for adding field names that were not originally part of the file, as well as for redefining field names. When the REDEFINE command is used, one or two bytes can be added to or deleted from a Table A entry, if the LEVEL or UPDATE option is changed. The amount of overhead required for a redefined field is computed according to the rules for the original definition (see ASTRPPG above). When you delete a field definition, all but two bytes are made available for reuse. </p>
	<p>		<p>
	If you are sure that field names will not be added to a file, you can use a multiplier closer to 1. The size of the multiplier is important if ATRPG comes out to be just over one page. A one-page attribute section of Table A provides much better performance than a multiple-page section. This performance difference can be seen in the amount of disk I/O required to compile a User Language request or Host Language Interface call that refers to many fields. </p>		If you are sure that field names will not be added to a file, you can use a multiplier closer to 1. The size of the multiplier is important if ATRPG comes out to be just over one page. A one-page attribute section of Table A provides much better performance than a multiple-page section. This performance difference can be seen in the amount of disk I/O required to compile a User Language request or [[Media:M204 HLIReference V75.pdf\|Host Language Interface]] call that refers to many fields. </p>
	<p class="note"><b>Note:</b>		<p class="note"><b>Note:</b>
	The product of ATRPG and ASTRPPG must not exceed 4000.</p>		The product of ATRPG and ASTRPPG must not exceed 4000.</p>

JAL at 20:01, 5 December 2014

2014-12-05T20:01:19Z

← Older revision		Revision as of 20:01, 5 December 2014
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	<tr>		<tr>
	<td>Ordered Index</td>		<td nowrap>Ordered Index</td>
	<td>Stored in Table D, is composed of the Ordered Index B-tree, which indexes ORDERED fields, plus a secondary index (located in Table D) containing Table B record numbers pointed to by Btree entries.</td>		<td>Stored in Table D, is composed of the Ordered Index B-tree, which indexes ORDERED fields, plus a secondary index (located in Table D) containing Table B record numbers pointed to by Btree entries.</td>
	~~</tr>~~

	~~<tr>~~
	~~<td colspan="2">In addition to these tables, some free space might be available to the file on unassigned pages in a free-space pool.</td>~~
	</tr>		</tr>
	</table>		</table>
			<p>
			In addition to these tables, some free space might be available to the file on unassigned pages in a free-space pool.</p>

	====FRV attribute entries====		====FRV attribute entries====

ELowell at 18:48, 12 May 2014

2014-05-12T18:48:15Z

← Older revision		Revision as of 18:48, 12 May 2014
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	<ul>		<ul>
	<li>If you have <var>[[Field design ~~(File management)~~#BLOB.2C CLOB and MINLOBE attributes\|MINLOBE]]</var> set, ignore large objects smaller than this number.</li>		<li>If you have <var>[[Field design#BLOB.2C CLOB.2C and MINLOBE attributes\|MINLOBE]]</var> set, ignore large objects smaller than this number.</li>

	<li>Be sure to take that (along with the large object header) into account when sizing Tables B and X.</li>		<li>Be sure to take that (along with the large object header) into account when sizing Tables B and X.</li>

DmeWiccan: Automatically generated page update

2014-05-09T22:45:48Z

Automatically generated page update

← Older revision		Revision as of 22:45, 9 May 2014
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	</div> <!-- end of toclimit div -->		</div> <!-- end of toclimit div -->

	[[Category:~~File management~~]]		[[Category:Model 204 files]]

JAL: /* Calculating ASTRPPG */

2014-02-20T22:33:55Z

Calculating ASTRPPG

← Older revision		Revision as of 22:33, 20 February 2014
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	<tr class="head">		<tr class="head">
	<th>Field</th>		<th>Field</th>
	<th>LEN + 2[[#fldnames-~~fnote~~\|<sup>[1]</sup>]]</th>		<th>LEN + 2[[#fldnames-fn1\|<sup>[1]</sup>]]</th>
	<th>ANY + UP[[#fldnames-~~fnote~~\|<sup>[2]</sup>]]</th>		<th>ANY + UP[[#fldnames-fn2\|<sup>[2]</sup>]]</th>
	<th>COD/FRV</th>		<th>COD/FRV</th>
	<th>OCC</th>		<th>OCC</th>
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	<td align="right">5</td>		<td align="right">5</td>
	<td align="right">3</td>		<td align="right">3</td>
	<td align="right">3[[#fldnames-~~fnote~~\|<sup>[3]</sup>]]</td>		<td align="right">3[[#fldnames-fn3\|<sup>[3]</sup>]]</td>
	<td align="right">3</td>		<td align="right">3</td>
	<td> </td>		<td> </td>
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	</table>		</table>

	<div id="fldnames-~~fnote~~"></div>		<div id="fldnames-fn1"></div>

	:<b>1</b>   LEN is the length of the field name.		:<b>1</b>   LEN is the length of the field name.

			<div id="fldnames-fn2"></div>
	:<b>2</b>   ANY refers to the two bytes required from page 3-5. UP refers to the one byte required for UPDATE IN PLACE fields.		:<b>2</b>   ANY refers to the two bytes required from page 3-5. UP refers to the one byte required for UPDATE IN PLACE fields.

			<div id="fldnames-fn3"></div>
	:<b>3</b>   Because only a small number of values in SSN start with a zero, this field does not have any effect on Table A space estimates.		:<b>3</b>   Because only a small number of values in SSN start with a zero, this field does not have any effect on Table A space estimates.

JAL: /* Calculating ASTRPPG */ footnote fix

2014-02-20T22:30:24Z

Calculating ASTRPPG: footnote fix

← Older revision		Revision as of 22:30, 20 February 2014
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	===Calculating ASTRPPG===		===Calculating ASTRPPG===

	<table>		<table>
	<caption>FRV or CODED values</caption>		<caption>FRV or CODED values</caption>
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	<tr class="head">		<tr class="head">
	<th>Field</th>		<th>Field</th>
	<th>LEN + 2[[#~~File Size Calculation~~\|<sup>1</sup>]]</th>		<th>LEN + 2[[#fldnames-fnote\|<sup>[1]</sup>]]</th>
	<th>ANY + UP[[#~~File Size Calculation~~\|<sup>2</sup>]]</th>		<th>ANY + UP[[#fldnames-fnote\|<sup>[2]</sup>]]</th>
	<th>COD/FRV</th>		<th>COD/FRV</th>
	<th>OCC</th>		<th>OCC</th>
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	<td align="right">5</td>		<td align="right">5</td>
	<td align="right">3</td>		<td align="right">3</td>
	<td align="right">(3)[[#~~File Size Calculation~~\|<sup>3</sup>]]</td>		<td align="right">3[[#fldnames-fnote\|<sup>[3]</sup>]]</td>
	<td align="right">3</td>		<td align="right">3</td>
	<td> </td>		<td> </td>
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	</table>		</table>

	<div id="~~File size calculation~~"></div>		<div id="fldnames-fnote"></div>

	:<b>1</b>  LEN is the length of the field name.		:<b>1</b>   LEN is the length of the field name.

	:<b>2</b>  ANY refers to the two bytes required from page 3-5. UP refers to the one byte required for UPDATE IN PLACE fields.		:<b>2</b>   ANY refers to the two bytes required from page 3-5. UP refers to the one byte required for UPDATE IN PLACE fields.

	:<b>3</b>  Because only a small number of values in SSN start with a zero, this field does not have any effect on Table A space estimates.		:<b>3</b>   Because only a small number of values in SSN start with a zero, this field does not have any effect on Table A space estimates.

	<p><b>Calculations</b></p>		<p><b>Calculations</b></p>
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	<b>ASTRPPG</b> <span class="squareb">=</span> 6144/L <span class="squareb">=</span> 6144/7 <span class="squareb">=</span> 877.7 <span class="squareb">=</span> <b>877</b> (rounded down)		<b>ASTRPPG</b> <span class="squareb">=</span> 6144/L <span class="squareb">=</span> 6144/7 <span class="squareb">=</span> 877.7 <span class="squareb">=</span> <b>877</b> (rounded down)
	</p>		</p>

	===Calculating ATRPG===		===Calculating ATRPG===
	<p>		<p>