LDKBMWNG parameter: Difference between revisions
| Line 4: | Line 4: | ||
<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 <code>0.5*<var>[[NUMBUFG_parameter|NUMBUFG]]</var>< | <p>(version 7.5 and higher) A minimum of <code>0.5*NUMBUFG</code>.</p> | ||
The minimum size of <var>[[NUMBUFG_parameter|NUMBUFG]]</var> is determined by this formula: | |||
<p class="code">NLRUQG * ((NSERVS + NSUBTKS) * MAXOBUF + 15)</p> | |||
If the current setting of NUMBUFG exceeds this value and the value is a multiple of NLRUQG, no further adjustments 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: | |||
<ul> | <ul> | ||
<li> | <li> | ||
Revision as of 21:01, 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.The minimum size of NUMBUFG is determined by this formula:
NLRUQG * ((NSERVS + NSUBTKS) * MAXOBUF + 15)
If the current setting of NUMBUFG exceeds this value and the value is a multiple of NLRUQG, no further adjustments are made.
Following that, if a value for LDKBMWNG is specified in CCAIN and that value 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
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.
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.