LDKBMWNG parameter: Difference between revisions

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<dl>
<dl>
<dt>Default value
<dt>Default value
<dd>(version 7.4) The value of <var>[[LDKBMWND_parameter|LDKBMWND]]</var> parameter, if set; otherwise, a value of 3.
<dd>V7.4: The value of <var>[[LDKBMWND_parameter|LDKBMWND]]</var>, if set; otherwise, a value of 3  
<p>(version 7.5 and higher) A minimum of <code>0.5*NUMBUFG</code>.</p>   
<p>V7.5 and higher: A minimum of <code>0.5*NUMBUFG</code></p>   


Before the value of <var>LDKBMWNG</var> is adjusted or recalculated, the minimum size of <var>[[NUMBUFG_parameter|NUMBUFG]]</var> must first be determined by this formula:  
Before the value of <var>LDKBMWNG</var> is adjusted or recalculated, the minimum size of <var>[[NUMBUFG parameter|NUMBUFG]]</var> must first be determined by this formula:  
<p class="code">NLRUQG * ((NSERVS + NSUBTKS) * MAXOBUF + 15)</p>  
<p class="code">NLRUQG * ((NSERVS + NSUBTKS) * MAXOBUF + 15)</p>  


If the current setting of <var>NUMBUFG</var> exceeds this value and the value is a multiple of <var>NLRUQG</var>, no further adjustments to <var>NUMBUFG</var> are made.   
If the current setting of <var>NUMBUFG</var> exceeds this value and is a multiple of <var>[[NLRUQG parameter|NLRUQG]]</var>, no further adjustments to <var>NUMBUFG</var> are made.   


Following that, if a value for <var>LDKBMWNG</var> is specified in CCAIN and that value is greater than <code>0.5*NUMBUFG</code>, the value can still be adjusted:
Following that, if a value for <var>LDKBMWNG</var> is specified in CCAIN and is greater than <code>0.5*NUMBUFG</code>, the value can still be adjusted:
<ul>
<ul>
<li>
<li>The final value must be an even multiple of <var>NLRUQG</var></li>
The final value must be an even multiple of <var>NLRUQG</var>
 
</li>
<li>The final value must <i>not</i> 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>
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>  
</ul>
</ul>
<dt>Parameter type
<dt>Parameter type
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==Description==
==Description==
<p>
<p>
An anticipatory write window that starts writes for any modified buffers that enter the window.</p>
<var>LDKBMWNG</var> specifies an anticipatory write window that starts writes for any modified ATB (above the bar) buffers that enter the window.</p>
<p>
<p>
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>
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>
<p>
 
Refer to [[Performance monitoring and tuning#Disk buffer monitor statistics and parameters|Disk buffer monitor statistics and parameters]] and [[Defining the runtime environment (CCAIN)#Managing ATB storage with NUMBUFG|Managing ATB storage with NUMBUFG]] for more information.  </p>
==See also==
<ul>
<li>[[Performance monitoring and tuning#Disk buffer monitor statistics and parameters|Disk buffer monitor statistics and parameters]] </li>
 
<li>[[Defining the runtime environment (CCAIN)#Managing ATB storage with NUMBUFG|Managing ATB storage with NUMBUFG]] </li>
 
<li><var>[[LDKBMWND parameter|LDKBMWND]]</var> </li>
</ul>


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

Latest revision as of 21:15, 22 September 2016

# of pages in DKBM-ATB anticipatory write window

Summary

Default value
V7.4: The value of LDKBMWND, if set; otherwise, a value of 3

V7.5 and higher: A minimum of 0.5*NUMBUFG

Before the value of LDKBMWNG is adjusted or recalculated, the minimum size of NUMBUFG must first be determined by this formula:

NLRUQG * ((NSERVS + NSUBTKS) * MAXOBUF + 15)

If the current setting of NUMBUFG exceeds this value and is a multiple of NLRUQG, no further adjustments to NUMBUFG are made.

Following that, if a value for LDKBMWNG is specified in CCAIN and is greater than 0.5*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

LDKBMWNG specifies an anticipatory write window that starts writes for any modified ATB (above the bar) buffers that enter the window.

When an anticipatory write for a modified buffer completes, the buffer is immediately reusable.

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).

See also

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