SEQOPT parameter: Difference between revisions
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Revision as of 16:43, 27 August 2013
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
The option for 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 described in more detail in the Model 204 User Language Manual and the Model 204 System Manager's Guide.
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)