SEQOPT parameter: Difference between revisions

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<dd>System
<dd>System
<dt>Where set
<dt>Where set
<dd>On User 0's parameter line
<dd>On User 0's parameter line, or reset by System Manager
<dt>Related products
<dt>Related products
<dd>All
<dd>All
<dt>Introduced
<dt>Introduced
<dd><var class="product">Model 204 V6.1</var> or earlier
<dd><var class="product">Model 204 V2.1</var> or earlier
</dl>
</dl>


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<var>SEQOPT</var> must be either zero or 1. If the default value of zero is used, the prefetch feature is disabled. If a value of 1 is specified, the prefetch feature is enabled.  </p>
<var>SEQOPT</var> must be either zero or 1. If the default value of zero is used, the prefetch feature is disabled. If a value of 1 is specified, the prefetch feature is enabled.  </p>
<p>
<p>
The prefetch feature can produce performance improvements for applications containing <var>FOR EACH RECORD</var> statements. The prefetch feature is also described in [[Performance monitoring and tuning#Prefetch feature|Prefetch feature]].</p>
The prefetch feature can produce performance improvements for applications containing <var>[[Record_loops#FOR_EACH_RECORD_statement|FOR EACH RECORD]]</var> statements. The prefetch feature is also described in [[Performance monitoring and tuning#Prefetch feature|Prefetch feature]].</p>
<p>
<p>
The prefetch feature can also be controlled with the <var>RESET</var> command issued by a user having system manager privileges.</p>
The prefetch feature can also be controlled with the <var>[[RESET_command|RESET]]</var> command issued by a user having system manager privileges.</p>
<p>
<p>
Use of the prefetch feature requires that the <var>[[MAXBUF parameter|MAXBUF]]</var> parameter be set large enough to accommodate the look-ahead reads. Without this setting, performance might worsen. The specification for the <var>MAXBUF</var> parameter is calculated by the following formula:  </p>
Use of the prefetch feature requires that the <var>[[NUMBUFG parameter|NUMBUFG]]</var> or the <var>[[MAXBUF parameter|MAXBUF]]</var> parameter be set large enough to accommodate the look-ahead reads. Without this setting, performance might worsen.  
<p class="code">MAXBUF = NUSERS * (4 + 2 * (Maximum FOR EACH RECORD loop nest level)
</p>
</p>


[[Category:System parameters]]
[[Category:System parameters]]
[[Category:Parameters]]
[[Category:Parameters]]

Latest revision as of 09:55, 30 May 2017

Sequential processing options

Summary

Default value
0
Parameter type
System
Where set
On User 0's parameter line, or reset by System Manager
Related products
All
Introduced
Model 204 V2.1 or earlier

Description

Enables or disables the prefetch (look-ahead read) feature.

SEQOPT must be either zero or 1. If the default value of zero is used, the prefetch feature is disabled. If a value of 1 is specified, the prefetch feature is enabled.

The prefetch feature can produce performance improvements for applications containing FOR EACH RECORD statements. The prefetch feature is also described in Prefetch feature.

The prefetch feature can also be controlled with the RESET command issued by a user having system manager privileges.

Use of the prefetch feature requires that the NUMBUFG or the MAXBUF parameter be set large enough to accommodate the look-ahead reads. Without this setting, performance might worsen.