mirror of
https://github.com/berkeleydb/libdb.git
synced 2024-11-16 17:16:25 +00:00
129 lines
6.5 KiB
HTML
129 lines
6.5 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
|
||
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
||
<html xmlns="http://www.w3.org/1999/xhtml">
|
||
<head>
|
||
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
|
||
<title>set_cachesize</title>
|
||
<link rel="stylesheet" href="apiReference.css" type="text/css" />
|
||
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
|
||
<link rel="start" href="index.html" title="Berkeley DB C API Reference" />
|
||
<link rel="up" href="configuration_reference.html" title="Appendix D. DB_CONFIG Parameter Reference" />
|
||
<link rel="prev" href="repmgr_site_parameter.html" title="repmgr_site" />
|
||
<link rel="next" href="set_cache_max_parameter.html" title="set_cache_max" />
|
||
</head>
|
||
<body>
|
||
<div xmlns="" class="navheader">
|
||
<div class="libver">
|
||
<p>Library Version 11.2.5.3</p>
|
||
</div>
|
||
<table width="100%" summary="Navigation header">
|
||
<tr>
|
||
<th colspan="3" align="center">set_cachesize</th>
|
||
</tr>
|
||
<tr>
|
||
<td width="20%" align="left"><a accesskey="p" href="repmgr_site_parameter.html">Prev</a> </td>
|
||
<th width="60%" align="center">Appendix D. DB_CONFIG Parameter Reference</th>
|
||
<td width="20%" align="right"> <a accesskey="n" href="set_cache_max_parameter.html">Next</a></td>
|
||
</tr>
|
||
</table>
|
||
<hr />
|
||
</div>
|
||
<div class="sect1" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h2 class="title" style="clear: both"><a id="set_cachesize_parameter"></a>set_cachesize</h2>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
Sets the size of the shared memory buffer pool — that is, the cache.
|
||
The cache should be the size of the normal working data set of the
|
||
application, with some small amount of additional memory for unusual
|
||
situations. (Note: the working set is not the same as the number of
|
||
pages accessed simultaneously, and is usually much larger.)
|
||
</p>
|
||
<p>
|
||
The value specified for this parameter is the
|
||
<span class="emphasis"><em>maximum</em></span> value that your application
|
||
will be able to use for your in-memory cache. If your
|
||
application does not have enough data to fill up the amount
|
||
of space specified here, then your application will only
|
||
use the amount of memory required by the data that your
|
||
application does have.
|
||
</p>
|
||
<p>
|
||
For the DB, the default cache size is 8MB. You cannot specify a
|
||
cache size value of less than 100KB.
|
||
</p>
|
||
<p>
|
||
Any cache size less than 500MB is automatically increased
|
||
by 25% to account for cache overhead; cache sizes larger
|
||
than 500MB are used as specified. The maximum size of a
|
||
single cache is 4GB on 32-bit systems and 10TB on 64-bit
|
||
systems. (All sizes are in powers-of-two, that is, 256KB
|
||
is 2^18 not 256,000.)
|
||
</p>
|
||
<p>
|
||
It is possible to specify cache sizes large enough they
|
||
cannot be allocated contiguously on some architectures. For example,
|
||
some releases of Solaris limit the amount of memory that may be
|
||
allocated contiguously by a process. If <span class="bold"><strong>ncache</strong></span> is 0 or 1, the cache will be allocated
|
||
contiguously in memory. If it is greater than 1, the cache will be
|
||
split across <span class="bold"><strong>ncache</strong></span> separate regions,
|
||
where the <span class="bold"><strong>region size</strong></span> is equal to the
|
||
initial cache size divided by <span class="bold"><strong>ncache</strong></span>.
|
||
</p>
|
||
<p>
|
||
The cache size supplied to this parameter will be
|
||
rounded to the nearest multiple of the region size and may not
|
||
be larger than the maximum possible cache size configured for your
|
||
application (use the
|
||
<a class="xref" href="set_cache_max_parameter.html" title="set_cache_max">set_cache_max</a>
|
||
to do this). The <span class="bold"><strong>ncache</strong></span>
|
||
parameter is ignored when resizing the cache.
|
||
</p>
|
||
<p>
|
||
The syntax of this parameter in the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file is a
|
||
single line with the string
|
||
<code class="literal">set_cachesize</code>, one or more whitespace
|
||
characters, and the initial cache size specified in three
|
||
parts: the gigabytes of cache, the additional bytes of
|
||
cache, and the number of caches, also separated by
|
||
whitespace characters. For example:
|
||
</p>
|
||
<pre class="programlisting">set_cachesize 2 524288000 1</pre>
|
||
<p>
|
||
Creates a single 2.5GB physical cache.
|
||
</p>
|
||
<p>
|
||
Note that this parameter is ignored unless it is specified
|
||
before you initially create your environment, or you
|
||
re-create your environment after changing it.
|
||
</p>
|
||
<p>
|
||
For more information, see
|
||
<a class="xref" href="envset_cachesize.html" title="DB_ENV->set_cachesize()">DB_ENV->set_cachesize()</a>.
|
||
</p>
|
||
</div>
|
||
<div class="navfooter">
|
||
<hr />
|
||
<table width="100%" summary="Navigation footer">
|
||
<tr>
|
||
<td width="40%" align="left"><a accesskey="p" href="repmgr_site_parameter.html">Prev</a> </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="u" href="configuration_reference.html">Up</a>
|
||
</td>
|
||
<td width="40%" align="right"> <a accesskey="n" href="set_cache_max_parameter.html">Next</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td width="40%" align="left" valign="top">repmgr_site </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="h" href="index.html">Home</a>
|
||
</td>
|
||
<td width="40%" align="right" valign="top"> set_cache_max</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</body>
|
||
</html>
|