MAXBUF parameter: Difference between revisions
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<dd><var class="product">Model 204 V6.1</var> or earlier | <dd><var class="product">Model 204 V6.1</var> or earlier | ||
</dl> | </dl> | ||
==Description== | ==Description== | ||
<p>The maximum number of in-memory file page buffers that can be allocated during <var class="product">Model 204</var> initialization</p> | <p> | ||
<p>The actual number of pages allocated to the disk buffer pool can be identified by viewing the parameter NUMBUF.</p> | The maximum number of in-memory file page buffers that can be allocated during <var class="product">Model 204</var> initialization</p> | ||
<p>If NLRUQ is set greater than 1, then the value of MAXBUF is rounded up to a multiple of NLRUQ. The maximum setting is 300000. Also, you must set XMEMOPT=X'02' to get more than about 15000-18000 or so actually allocated to NUMBUF.</p> | <p> | ||
<p>If MAXBUF is set to a value less than MINBUF, MAXBUF is automatically reset to the value of MINBUF and the following message is issued: </p> | The actual number of pages allocated to the disk buffer pool can be identified by viewing the parameter <var>[[NUMBUF parameter|NUMBUF]]</var>.</p> | ||
<p> | |||
If <var>[[NLRUQ parameter|NLRUQ]]</var> is set greater than 1, then the value of <var>MAXBUF</var> is rounded up to a multiple of <var>NLRUQ</var>. The maximum setting is 300000. Also, you must set XMEMOPT=X'02' to get more than about 15000-18000 or so actually allocated to <var>NUMBUF</var>.</p> | |||
<p> | |||
If <var>MAXBUF</var> is set to a value less than <var>MINBUF</var>, <var>MAXBUF</var> is automatically reset to the value of <var>MINBUF</var> and the following message is issued: </p> | |||
<p class="code">M204.1190: MAXBUF SET TO SAME VALUE AS MINBUF -%C | <p class="code">M204.1190: MAXBUF SET TO SAME VALUE AS MINBUF -%C | ||
</p> | </p> | ||
<p>You can use the MONITOR DISKBUFF command to display, from each table of each file, the number of pages that are currently located in the disk buffers.</p> | <p> | ||
<p>If the prefetch feature is enabled (SEQOPT=1), then the MAXBUF parameter must be resized based on the following formula: </p> | You can use the <code>MONITOR DISKBUFF</code> command to display, from each table of each file, the number of pages that are currently located in the disk buffers.</p> | ||
<p> | |||
If the prefetch feature is enabled (SEQOPT=1), then the <var>MAXBUF</var> parameter must be resized based on the following formula: </p> | |||
<p class="code">MAXBUF = NUSERS * (4 + 2 * (Maximum FOR EACH RECORD loop nest level)) | <p class="code">MAXBUF = NUSERS * (4 + 2 * (Maximum FOR EACH RECORD loop nest level)) | ||
</p> | </p> | ||
<p>The prefetch feature is described in | <p> | ||
The prefetch feature is described in [[Record loops#The prefetch (look-ahead read) feature|The prefetch (look-ahead read) feature]] and in the <var class="book">Rocket Model 204 System Manager's Guide</var>. </p> | |||
[[Category:System parameters]] | [[Category:System parameters]] | ||
[[Category:Parameters]] | [[Category:Parameters]] | ||
Revision as of 21:21, 15 April 2014
Maximum number of buffers
Summary
- Default value
- 256
- Parameter type
- System
- Where set
- On User 0's parameter line
- Related products
- All
- Introduced
- Model 204 V6.1 or earlier
Description
The maximum number of in-memory file page buffers that can be allocated during Model 204 initialization
The actual number of pages allocated to the disk buffer pool can be identified by viewing the parameter NUMBUF.
If NLRUQ is set greater than 1, then the value of MAXBUF is rounded up to a multiple of NLRUQ. The maximum setting is 300000. Also, you must set XMEMOPT=X'02' to get more than about 15000-18000 or so actually allocated to NUMBUF.
If MAXBUF is set to a value less than MINBUF, MAXBUF is automatically reset to the value of MINBUF and the following message is issued:
M204.1190: MAXBUF SET TO SAME VALUE AS MINBUF -%C
You can use the MONITOR DISKBUFF command to display, from each table of each file, the number of pages that are currently located in the disk buffers.
If the prefetch feature is enabled (SEQOPT=1), then the MAXBUF parameter must be resized based on the following formula:
MAXBUF = NUSERS * (4 + 2 * (Maximum FOR EACH RECORD loop nest level))
The prefetch feature is described in The prefetch (look-ahead read) feature and in the Rocket Model 204 System Manager's Guide.