SEQOPT parameter: Difference between revisions
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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 | 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> | ||
<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</var> command issued by a user having system manager privileges.</p> | ||
Revision as of 23:05, 30 October 2014
Sequential processing options
Summary
- Default value
- 0
- Parameter type
- System
- Where set
- On User 0's parameter line
- Related products
- All
- Introduced
- Model 204 V6.1 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 MAXBUF parameter be set large enough to accommodate the look-ahead reads. Without this setting, performance might worsen. The specification for the MAXBUF parameter is calculated by the following formula:
MAXBUF = NUSERS * (4 + 2 * (Maximum FOR EACH RECORD loop nest level)