NUMBUFG parameter: Difference between revisions

From m204wiki
Jump to navigation Jump to search
m (add 7.7 change)
 
(9 intermediate revisions by one other user not shown)
Line 19: Line 19:
<ul>
<ul>
<li>Prior to version 7.7 of Model&nbsp;204:  
<li>Prior to version 7.7 of Model&nbsp;204:  
<p><var>NUMBUFG</var> specifies the number of buffer pool buffers built ATB, and the number of buffer pool buffers built BTB is based on the setting of <var>MINBUF</var>, <var>MAXBUF</var>, and <var>SPCORE</var>.</p></li>
<p>
<var>NUMBUFG</var> specifies the number of buffer pool buffers built ATB, while the number of buffer pool buffers built BTB is based on the setting of <var>[[MINBUF parameter|MINBUF]]</var>, <var>[[MAXBUF parameter|MAXBUF]]</var>, and <var>[[SPCORE parameter|SPCORE]]</var>.</p></li>


<li>As of version 7.7:  
<li>As of version 7.7:  
<p>If <var>NUMBUFG</var> is specified, no buffer pool buffers are built BTB; all buffers are ATB. The <var>MINBUF</var> parameter is automatically reset to 0, and <var>MAXBUF</var> and <var>SPCORE</var> are ignored. </p></li>
<p>
If <var>NUMBUFG</var> is specified, no buffer pool buffers are built BTB; all buffers are ATB. Model&nbsp;204 obtains exactly the <var>NUMBUFG</var> number of buffers. </p>
<p>
In this case, <var>NUMBUFG</var> essentially replaces the BTB parameters: <var>NUMBUF</var> and <var>MINBUF</var> are automatically reset to 0, and <var>MAXBUF</var> and <var>SPCORE</var> are ignored. </p>
</li>
</ul>
</ul>


===Setting NUMBUFG===
<p>
<p>
The maximum number of buffers is <code>2**31/3</code>, or <code>715,827,882</code>, which limits buffer pools to 4.2 terabytes or less.</p>
The maximum number of buffers is <code>2**31/3</code>, or <code>715,827,882</code>, which limits buffer pools to 4.2 terabytes or less.</p>
<p>
<p>
For background information, see [[Defining the runtime environment (CCAIN)#Disk buffers and Model 204 storage|Disk buffers and Model 204 storage]]. </p>
The minimum number of ATB buffers is: </p>
<p class="code">[[NLRUQG parameter|NLRUQG]] * (([[NSERVS parameter|NSERVS]] + [[NSUBTKS parameter|NSUBTKS]]) * [[MAXOBUF parameter|MAXOBUF]] + 15)
</p>
<p>
If you set <var>NUMBUFG</var> to a value lower than the minimum, the value is reset to the calculated value and you receive messages like the following: </p>
<p class="code">&#42;** M204.2756: NUMBUFG reset to NLRUQG * ((NSERVS + NSUBTKS) * MAXOBUF + 15)
              = 1 * ((2+9) * 4 + 15) = 59                         
&#42;** M204.0075: Initialization completed.  Buffers = 0+59
</p>
<blockquote class="note"><b>Note:</b>
<p>If you set <var>NUMBUFG</var> greater than 0: </p>
<ul>
<li>The X'02' bit of the <var>[[XMEMOPT parameter|XMEMOPT]]</var> parameter (the default), must also be set. </li>
 
<li>The [[File Load utility: FLOD and FILELOAD commands|FLOD and FILELOAD commands]] and [[Fast/Reload]] are not available due to 64-bit addressing conflicts. This particular restriction is removed in V7.7 and later releases.
</ul>
</blockquote>
 
==See also==
For more information about setting <var>NUMBUFG</var>, see [[Defining the runtime environment (CCAIN)#Using 64-bit addressing and Above the Bar (ATB) storage|Using 64-bit addressing and Above the Bar (ATB) storage]].  


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

Latest revision as of 14:49, 26 August 2020

Number of above-the-bar buffers

Summary

Default value
0
Parameter type
System
Where set
Not resettable
Related products
All
Introduced
Model 204 V7.1

Description

Allocate this number of buffer pool buffers above the bar (ATB).

  • Prior to version 7.7 of Model 204:

    NUMBUFG specifies the number of buffer pool buffers built ATB, while the number of buffer pool buffers built BTB is based on the setting of MINBUF, MAXBUF, and SPCORE.

  • As of version 7.7:

    If NUMBUFG is specified, no buffer pool buffers are built BTB; all buffers are ATB. Model 204 obtains exactly the NUMBUFG number of buffers.

    In this case, NUMBUFG essentially replaces the BTB parameters: NUMBUF and MINBUF are automatically reset to 0, and MAXBUF and SPCORE are ignored.

Setting NUMBUFG

The maximum number of buffers is 2**31/3, or 715,827,882, which limits buffer pools to 4.2 terabytes or less.

The minimum number of ATB buffers is:

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

If you set NUMBUFG to a value lower than the minimum, the value is reset to the calculated value and you receive messages like the following:

*** M204.2756: NUMBUFG reset to NLRUQG * ((NSERVS + NSUBTKS) * MAXOBUF + 15) = 1 * ((2+9) * 4 + 15) = 59 *** M204.0075: Initialization completed. Buffers = 0+59

Note:

If you set NUMBUFG greater than 0:

  • The X'02' bit of the XMEMOPT parameter (the default), must also be set.
  • The FLOD and FILELOAD commands and Fast/Reload are not available due to 64-bit addressing conflicts. This particular restriction is removed in V7.7 and later releases.

See also

For more information about setting NUMBUFG, see Using 64-bit addressing and Above the Bar (ATB) storage.