LDKBMWNG parameter: Difference between revisions
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<dt>Default value | <dt>Default value | ||
<dd>(version 7.4) The value of <var>[[LDKBMWND_parameter|LDKBMWND]]</var>, if set; otherwise, a value of 3. | <dd>(version 7.4) The value of <var>[[LDKBMWND_parameter|LDKBMWND]]</var>, if set; otherwise, a value of 3. | ||
<p>(version 7.5 and higher) A minimum of 0.5 * <var>[[NUMBUFG_parameter|NUMBUFG]]</var>.</p> | <p>(version 7.5 and higher) A minimum of <code>0.5*<var>[[NUMBUFG_parameter|NUMBUFG]]</var></code>.</p> | ||
<p>NUMBUFG will first be adjusted (rounded up) to be an even multiple of NLRUQG. Following that, if a value for LDKBMWNG is specified in CCAIN and that value is greater than .5*NUMBUFG, the value can still be adjusted:</p> | <p> | ||
<var>NUMBUFG</var> will first be adjusted (rounded up) to be an even multiple of <var>[[NLRUQG parameter|NLRUQG]]</var>. Following that, if a value for <var>LDKBMWNG</var> is specified in CCAIN and that value is greater than <code>.5*NUMBUFG</code>, the value can still be adjusted:</p> | |||
<ul> | <ul> | ||
<li> | <li> | ||
The final value must be an even multiple of NLRUQG | The final value must be an even multiple of <var>NLRUQG</var> | ||
</li> | </li> | ||
<li> | <li> | ||
The final value must not be greater than NUMBUFG minus the total number of buffers that might possibly be open at any one time; that is: < | The final value must not be greater than <var>NUMBUFG</var> minus the total number of buffers that might possibly be open at any one time; that is: <p class="code">NUMBUFG - (((NSERVS+NSUBTKS)*MAXOBUF)+14)*NLRUQG </p> | ||
</li> | </li> | ||
</ul> | </ul> | ||
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When an anticipatory write for a modified buffer completes, the buffer is immediately reusable. </p> | When an anticipatory write for a modified buffer completes, the buffer is immediately reusable. </p> | ||
<p> | <p> | ||
If <var>[[NLRUQG_parameter|NLRUQG]]</var> is set greater than 1, | If <var>[[NLRUQG_parameter|NLRUQG]]</var> is set greater than 1, the value of <var>LDKBMWNG</var> is rounded up to a multiple of <var>NLRUQG</var>. <var>LDKBMWNG</var> has a minimum size of one (1). </p> | ||
<p> | <p> | ||
High values of <var>LDKBMWNG</var> might unnecessarily increase the number of writes done (measured by the DKWR statistic). Low values might cause excessive waiting for buffers (measured by the DKSWAIT statistic).</p> | High values of <var>LDKBMWNG</var> might unnecessarily increase the number of writes done (measured by the DKWR statistic). Low values might cause excessive waiting for buffers (measured by the DKSWAIT statistic).</p> | ||
Revision as of 18:07, 28 April 2016
# of pages in DKBM-ATB anticipatory write window
Summary
- Default value
- (version 7.4) The value of LDKBMWND, if set; otherwise, a value of 3.
(version 7.5 and higher) A minimum of
0.5*NUMBUFG.NUMBUFG will first be adjusted (rounded up) to be an even multiple of NLRUQG. Following that, if a value for LDKBMWNG is specified in CCAIN and that value is greater than
.5*NUMBUFG, the value can still be adjusted:- The final value must be an even multiple of NLRUQG
-
The final value must not be greater than NUMBUFG minus the total number of buffers that might possibly be open at any one time; that is:
NUMBUFG - (((NSERVS+NSUBTKS)*MAXOBUF)+14)*NLRUQG
- Parameter type
- System
- Where set
- On User 0's parameter line by system manager
- Related products
- All
- Introduced
- Model 204 V7.4
Description
An anticipatory write window that starts writes for any modified buffers that enter the window.
When an anticipatory write for a modified buffer completes, the buffer is immediately reusable.
If NLRUQG is set greater than 1, the value of LDKBMWNG is rounded up to a multiple of NLRUQG. LDKBMWNG has a minimum size of one (1).
High values of LDKBMWNG might unnecessarily increase the number of writes done (measured by the DKWR statistic). Low values might cause excessive waiting for buffers (measured by the DKSWAIT statistic).
Refer to Disk buffer monitor statistics and parameters and Managing ATB storage with NUMBUFG for more information.