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<title>mod_mem_cache - Apache HTTP Server</title>
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<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
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<p class="apache">Apache HTTP Server Version 2.2</p>
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.2</a> > <a href="./">Modules</a></div>
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<div id="page-content">
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<div id="preamble"><h1>Apache Module mod_mem_cache</h1>
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<p><span>Available Languages: </span><a href="../en/mod/mod_mem_cache.html" title="English"> en </a> |
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<a href="../ja/mod/mod_mem_cache.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
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<a href="../ko/mod/mod_mem_cache.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Content cache keyed to URIs</td></tr>
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<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>mem_cache_module</td></tr>
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<tr><th><a href="module-dict.html#SourceFile">Source�File:</a></th><td>mod_mem_cache.c</td></tr></table>
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<p>This module <em>requires</em> the service of <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>. It acts as a support module for <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code> and provides a memory based storage manager.
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<code class="module"><a href="../mod/mod_mem_cache.html">mod_mem_cache</a></code> can be configured to operate in two
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modes: caching open file descriptors or caching objects in heap storage.
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<code class="module"><a href="../mod/mod_mem_cache.html">mod_mem_cache</a></code> is most useful when used to cache locally
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generated content or to cache backend server content for <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> configured for <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code> (aka <dfn>reverse proxy</dfn>).</p>
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<p>Content is stored in and retrieved from the cache using URI based
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keys. Content with access protection is not cached.</p>
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<div id="quickview"><h3 class="directives">Directives</h3>
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<li><img alt="" src="../images/down.gif" /> <a href="#mcachemaxobjectcount">MCacheMaxObjectCount</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#mcachemaxobjectsize">MCacheMaxObjectSize</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#mcachemaxstreamingbuffer">MCacheMaxStreamingBuffer</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#mcacheminobjectsize">MCacheMinObjectSize</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#mcacheremovalalgorithm">MCacheRemovalAlgorithm</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#mcachesize">MCacheSize</a></li>
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<li><code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code></li>
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<li><code class="module"><a href="../mod/mod_disk_cache.html">mod_disk_cache</a></code></li>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="MCacheMaxObjectCount" id="MCacheMaxObjectCount">MCacheMaxObjectCount</a> <a name="mcachemaxobjectcount" id="mcachemaxobjectcount">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The maximum number of objects allowed to be placed in the
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MCacheMaxObjectCount <var>value</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MCacheMaxObjectCount 1009</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_mem_cache</td></tr>
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<p>The <code class="directive">MCacheMaxObjectCount</code> directive sets the
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maximum number of objects to be cached. The value is used to create the
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open hash table. If a new object needs to be inserted in the cache and
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the maximum number of objects has been reached, an object will be
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removed to allow the new object to be cached. The object to be removed
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is selected using the algorithm specified by <code class="directive"><a href="#mcacheremovalalgorithm">MCacheRemovalAlgorithm</a></code>.</p>
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<div class="example"><h3>Example</h3><p><code>
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MCacheMaxObjectCount 13001
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="MCacheMaxObjectSize" id="MCacheMaxObjectSize">MCacheMaxObjectSize</a> <a name="mcachemaxobjectsize" id="mcachemaxobjectsize">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The maximum size (in bytes) of a document allowed in the
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MCacheMaxObjectSize <var>bytes</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MCacheMaxObjectSize 10000</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_mem_cache</td></tr>
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<p>The <code class="directive">MCacheMaxObjectSize</code> directive sets the
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maximum allowable size, in bytes, of a document for it to be considered
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<div class="example"><h3>Example</h3><p><code>
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MCacheMaxObjectSize 6400000
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<div class="note"><h3>Note</h3>
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<p>The value of <code class="directive">MCacheMaxObjectSize</code> must be
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greater than the value specified by the <code class="directive"><a href="#mcacheminobjectsize">MCacheMinObjectSize</a></code> directive.</p>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="MCacheMaxStreamingBuffer" id="MCacheMaxStreamingBuffer">MCacheMaxStreamingBuffer</a> <a name="mcachemaxstreamingbuffer" id="mcachemaxstreamingbuffer">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum amount of a streamed response to buffer in memory
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before declaring the response uncacheable</td></tr>
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MCacheMaxStreamingBuffer <var>size_in_bytes</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MCacheMaxStreamingBuffer the smaller of 100000 or MCacheMaxObjectSize</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_mem_cache</td></tr>
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<p>The <code class="directive">MCacheMaxStreamingBuffer</code> directive
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specifies the maximum number of bytes of a streamed response to
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buffer before deciding that the response is too big to cache.
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A streamed response is one in which the entire content is not
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immediately available and in which the <code>Content-Length</code>
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may not be known. Sources of streaming responses include proxied
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responses and the output of CGI scripts. By default, a streamed
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response will <em>not</em> be cached unless it has a
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<code>Content-Length</code> header. The reason for this is to
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avoid using a large amount of memory to buffer a partial response
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that might end up being too large to fit in the cache.
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The <code class="directive">MCacheMaxStreamingBuffer</code> directive allows
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buffering of streamed responses that don't contain a
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<code>Content-Length</code> up to the specified maximum amount of
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space. If the maximum buffer space is reached, the buffered
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content is discarded and the attempt to cache is abandoned.</p>
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<div class="note"><h3>Note:</h3>
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<p>Using a nonzero value for <code class="directive">MCacheMaxStreamingBuffer</code>
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will not delay the transmission of the response to the client.
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As soon as <code class="module"><a href="../mod/mod_mem_cache.html">mod_mem_cache</a></code> copies a block of streamed
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content into a buffer, it sends the block on to the next output
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filter for delivery to the client.</p>
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<div class="example"><p><code>
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# Enable caching of streamed responses up to 64KB:<br />
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MCacheMaxStreamingBuffer 65536
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="MCacheMinObjectSize" id="MCacheMinObjectSize">MCacheMinObjectSize</a> <a name="mcacheminobjectsize" id="mcacheminobjectsize">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum size (in bytes) of a document to be allowed in the
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MCacheMinObjectSize <var>bytes</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MCacheMinObjectSize 0</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_mem_cache</td></tr>
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<p>The <code class="directive">MCacheMinObjectSize</code> directive sets the
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minimum size in bytes of a document for it to be considered
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<div class="example"><h3>Example</h3><p><code>
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MCacheMinObjectSize 10000
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="MCacheRemovalAlgorithm" id="MCacheRemovalAlgorithm">MCacheRemovalAlgorithm</a> <a name="mcacheremovalalgorithm" id="mcacheremovalalgorithm">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The algorithm used to select documents for removal from the
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MCacheRemovalAlgorithm LRU|GDSF</code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MCacheRemovalAlgorithm GDSF</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_mem_cache</td></tr>
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<p>The <code class="directive">MCacheRemovalAlgorithm</code> directive specifies
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the algorithm used to select documents for removal from the cache.
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Two choices are available:</p>
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<dt><code>LRU</code> (Least Recently Used)</dt>
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<dd><code>LRU</code> removes the documents that have not been accessed
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for the longest time.</dd>
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<dt><code>GDSF</code> (GreadyDual-Size)</dt>
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<dd><code>GDSF</code> assigns a priority to cached documents based
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on the cost of a cache miss and the size of the document. Documents
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with the lowest priority are removed first.</dd>
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<div class="example"><h3>Example</h3><p><code>
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MCacheRemovalAlgorithm GDSF<br />
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MCacheRemovalAlgorithm LRU
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="MCacheSize" id="MCacheSize">MCacheSize</a> <a name="mcachesize" id="mcachesize">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The maximum amount of memory used by the cache in
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MCacheSize <var>KBytes</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MCacheSize 100</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_mem_cache</td></tr>
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<p>The <code class="directive">MCacheSize</code> directive sets the maximum
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amount of memory to be used by the cache, in KBytes (1024-byte units).
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If a new object needs to be inserted in the cache and the size of the
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object is greater than the remaining memory, objects will be removed
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until the new object can be cached. The object to be removed is
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selected using the algorithm specified by <code class="directive"><a href="#mcacheremovalalgorithm">MCacheRemovalAlgorithm</a></code>.</p>
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<div class="example"><h3>Example</h3><p><code>
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<div class="note"><h3>Note</h3>
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<p>The <code class="directive">MCacheSize</code> value must be greater than
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the value specified by the <code class="directive"><a href="#mcachemaxobjectsize">MCacheMaxObjectSize</a></code> directive.</p>
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<div class="bottomlang">
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<p><span>Available Languages: </span><a href="../en/mod/mod_mem_cache.html" title="English"> en </a> |
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<a href="../ja/mod/mod_mem_cache.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
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<a href="../ko/mod/mod_mem_cache.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
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</div><div id="footer">
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<p class="apache">Copyright 2006 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
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