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<title> Module mod_disk_cache</title>
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<!--Java sync-link--><h1 class="topictitle1"> Module mod_disk_cache</h1>
<div><p>This topic describes the module mod_disk_cache for HTTP Server
(powered by Apache).</p>
<div class="important"><span class="importanttitle">Important:</span> Information
for this topic supports the latest PTF levels for HTTP Server for i5/OS .
It is recommended that you install the latest PTFs to upgrade to the latest
level of the HTTP Server for i5/OS. Some of the topics documented here are
not available prior to this update. See <a href="http://www-03.ibm.com/servers/eserver/iseries/software/http/services/service.html" target="_blank">http://www.ibm.com/servers/eserver/iseries/software/http/services/service.htm</a> <img src="www.gif" alt="Link outside Information Center" /> for more information. </div>
<div class="section" id="rzaiemod_disk_cache__twodiscmain"><a name="rzaiemod_disk_cache__twodiscmain"><!-- --></a><h4 class="sectiontitle">Two Phase Disk Cache Maintenance</h4><p>The
server may take each iteration of the disk cache maintenance process through
one or two phases, depending on how much maintenance is needed. In the first
phase, the server will examine the file system directories for the disk cache
function and discard data that no longer complies with the current server
configuration settings. It will also discard unused or unmodified data according
to the criteria set by CacheGcClean or CacheGcUnused directives. File names
and expiration times for the remaining data will be collected and the total
amount of space allocated for them will be tallied. If the tally is above
the maximum disk storage limit (set by CacheSize), the server will go into
phase two. If the tally is at or below the maximum disk storage limit, the
server will stop the current iteration of the maintenance process. If the
server takes the current iteration into the second phase, information collected
in the first phase for the remaining data is sorted according to cache expiry
time. The server will then discard remaining data, by order of expiration
(soonest to latest), until the amount of allocated space is at or below the
maximum disk storage limit.</p>
<p>The following steps summarize the disk cache
maintenance process:</p>
<dl><dt class="dlterm">Phase One:</dt>
<dd><ol><li>Data files are examined, one by one, starting at the directory root specified
by CacheRoot.</li>
<li>Data files not complying with settings specified for CacheDirLevels, CacheDirLength,
CacheMinFileSize, and CacheMaxFileSize are discarded.</li>
<li>Unused or unmodified data matching the criteria set by CacheGcClean and
CacheGcUnused directives is discarded.</li>
<li>File names and expiration times for remaining data is collected.</li>
<li>The total amount of space allocated for remaining data is determined.
Phase two is entered if this total is greater than that specified by CacheSize.
If not, phase two is skipped and maintenance completes (until the next iteration).</li>
</ol>
</dd>
</dl>
<dl><dt class="dlterm">Phase Two:</dt>
<dd><ol><li>Information collected in phase one for remaining data is sorted according
to cache expiry times.</li>
<li>Data is discarded, by order of expiration (soonest to latest), until the
total amount of allocated space is at or below that specified by CacheSize.</li>
</ol>
</dd>
</dl>
<div class="note"><span class="notetitle">Note:</span> The server stops collecting information for remaining
data when it reaches the maximum amount of memory allowed for disk cache maintenance
(set by CacheGcMemUsage). If the server reaches this limit in phase one, it
may not have recorded enough information for phase two to bring the total
amount of space allocated for the cache down to the limit specified by the
CacheSize directive in one iteration of the disk cache maintenance process.
In this case, a warning message is written to the server log and the server
completes maintenance and waits for the next disk cache maintenance iteration.</div>
</div>
<p><strong>Directives</strong></p>
<ul><li><a href="#cachedirlength">CacheDirLength</a></li>
<li><a href="#cachedirlevels">CacheDirLevels</a></li>
<li><a href="#cachegcclean">CacheGcClean</a></li>
<li><a href="#cachegcdaily">CacheGcDaily</a></li>
<li><a href="#cachegcinterval">CacheGcInterval</a></li>
<li><a href="#directiveName">CacheGcMemUsage</a></li>
<li><a href="#cachegcunused">CacheGcUnused</a></li>
<li><a href="#cacheroot">CacheRoot</a></li>
<li><a href="#cachesize">CacheSize</a></li>
</ul>
</div>
<div class="hr" id="cachedirlength"><a name="cachedirlength"><!-- --></a><h2 class="topictitle2">CacheDirLength</h2>
<div>
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="void" border="0" rules="none"><tbody><tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Module">Module</a></strong>: mod_disk_cache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Syntax">Syntax</a></strong>: CacheDirLength <var class="varname">length</var></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Default">Default</a></strong>: CacheDirLength 2 </td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Context">Context</a></strong>: server config, virtual host</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Override">Override</a></strong>: none</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Origin">Origin</a></strong>: Apache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__UsageConsiderations">Usage Considerations</a></strong>: A LoadModule is required in
the configuration file prior to using the directive. The statement should
be as follows: <samp class="codeph">LoadModule disk_cache_module /QSYS.LIB/QHTTPSVR.LIB/QZSRCORE.SRVPGM</samp></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Example">Example</a></strong>: CacheDirLength 4</td>
</tr>
</tbody>
</table>
</div>
<p> The CacheDirLength directive specifies the number of characters in subdirectory
names used by the disk cache function to store data.</p>
<blockquote><dl><dt class="dlterm"><strong>Parameter</strong>: <em>length</em></dt>
<dd><ul><li>The <var class="varname">length</var> parameter specifies the number of characters
in subdirectory names used by the disk cache function. The specified value
multiplied by the value specified for the CacheDirLevels directive must be
less than or equal to 20.</li>
</ul>
</dd>
</dl>
</blockquote>
<p>If the values specified for CacheDirLevels and CacheDirLength are changed
once they have been used to cache data, the server will discard all existing
cache data when it runs disk cache maintenance since the file paths used to
store data no longer adhere to the new values. See the CacheGcDaily or CacheGcInterval
directives for more details on disk cache maintenance.</p>
<ul><li>This directive is used only if CacheRoot is set.</li>
</ul>
<div class="note"><span class="notetitle">Note:</span> HTTP Server (powered by Apache) does not support inheritance for the
CacheDirLength directive.</div>
</div>
</div>
<div class="hr" id="cachedirlevels"><a name="cachedirlevels"><!-- --></a><h2 class="topictitle2">CacheDirLevels</h2>
<div>
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="void" border="0" rules="none"><tbody><tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Module">Module</a></strong>: mod_disk_cache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Syntax">Syntax</a></strong>: CacheDirLevels <var class="varname">levels</var></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Default">Default</a></strong>: CacheDirLevels 3</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Context">Context</a></strong>: server config, virtual host</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Override">Override</a></strong>: none</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Origin">Origin</a></strong>: Apache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__UsageConsiderations">Usage Considerations</a></strong>: A LoadModule is required in
the configuration file prior to using the directive. The statement should
be as follows: <samp class="codeph">LoadModule disk_cache_module /QSYS.LIB/QHTTPSVR.LIB/QZSRCORE.SRVPGM</samp></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Example">Example</a></strong>: CacheDirLevels 3</td>
</tr>
</tbody>
</table>
</div>
<p> The CacheDirLevels directive specifies the number of directory levels
used by the disk cache function to store data.</p>
<blockquote><dl><dt class="dlterm"><strong>Parameter</strong>: <em>levels</em></dt>
<dd><ul><li> The <var class="varname">length</var> parameter specifies the number of directory
levels used by the disk cache function. The specified value multiplied by
the value specified for the CacheDirLength directive must be less than or
equal to 20.</li>
</ul>
<p>A hash algorithm is used to generate unique and seemingly random character
strings from hash keys (or URLs) provided for data stored in cache. These
character strings are used to build unique file system path names. Data is
stored in the file system using these path names, relative to the directory
root specified by the CacheRoot directive. This setting specifies how many
directory levels are used, while the CacheDirLength directives specifies the
length of each subdirectory name, with remaining characters simply used for
file names. The server uses the hash algorithm and directory levels to improve
the performance of the server when working with a potentially large number
of data files.</p>
</dd>
</dl>
<dl><dt class="dlterm"><strong>Example 1</strong></dt>
<dd><pre>CacheRoot /QOpenSys/QIBM/UserData/HTTPA/CacheRoot/MyCache
CacheDirLevels 3
CacheDirLength 1</pre>
<p> The above example indicates that a hash key
such as ftp://ibm.com/document.html may be used to build a directory path
such as <samp class="codeph">/x/3/_/9sj4t2svBA</samp> where <samp class="codeph">x</samp>, <samp class="codeph">3</samp>,
and <samp class="codeph">_</samp> are three subdirectory names (CacheDirLevels 3) each
having a length of one character (CacheDirLength 1). The remaining characters, <samp class="codeph">9sj4t2svBA</samp>,
are used for file names.</p>
</dd>
</dl>
<dl><dt class="dlterm"><strong>Example 2</strong></dt>
<dd><pre>CacheRoot /QOpenSys/QIBM/UserData/HTTPA/CacheRoot/MyCache
CacheDirLevels 5
CacheDirLength 2</pre>
<p> The above example indicates that the same
hash key described for example one (ftp://ibm.com/document.html) may be used
to build a directory path such as /x3/_9/sj/4t/2s/vBA where <samp class="codeph">x3</samp>, <samp class="codeph">_9</samp>, <samp class="codeph">sj</samp>, <samp class="codeph">4t</samp>,
and <samp class="codeph">2s</samp> are five subdirectory names (CacheDirLevels 5) each
having a length of two characters (CacheDirLength 2). The remaining characters, <samp class="codeph">vBA</samp>,
are used for file names.</p>
</dd>
</dl>
</blockquote>
<p>Directory paths generated in this process are relative to the directory
root defined by the CacheRoot directive. Therefore, for example one (above),
two files, one named <samp class="codeph">9sj4t2svBA.data</samp> and the other named <samp class="codeph">9sj4t2svBA.header</samp> will
be created to store data using the hash key <samp class="codeph">ftp://ibm.com/document.html</samp>.
Both files will reside within the <samp class="codeph">/QOpenSys/QIBM/UserData/HTTPA/CacheRoot/MyCache/x/3/_</samp> directory.
For example two (above), the two files will be named <samp class="codeph">vBA.data</samp> and <samp class="codeph">vBA.header</samp> and
will reside within the <samp class="codeph">/QOpenSys/QIBM/UserData/HTTPA/CacheRoot/MyCache/x3/_9/sj/4t/2s</samp> directory
using the same hash key.</p>
<p><strong>Directory length and level limits:</strong></p>
<p>Since the hash algorithm generates an exponential number of directories
using this schema, a limit must be set upon the values that CacheDirLevels
and CacheDirLength may have. The limits described as such:</p>
<pre> CacheDirLevels * CacheDirLength &lt;= 20</pre>
<p>The maximum number of directory levels multiplied by the maximum length
of each subdirectory must be less than or equal to 20. If not, the server
will fail to activate at startup. </p>
<p>If the values specified for CacheDirLevels and CacheDirLength are changed
once they have been used to cache data, the server will discard all existing
cache data when it runs disk cache maintenance since the file paths used to
store data no longer adhere to the new values. See the CacheGcDaily or CacheGcInterval
directives for more details on disk cache maintenance.</p>
<ul><li> This directive is used only if CacheRoot is set.</li>
</ul>
<div class="note"><span class="notetitle">Note:</span> HTTP Server (powered by Apache) does not support inheritance for the
CacheDirLevels directive.</div>
</div>
</div>
<div class="hr" id="cachegcclean"><a name="cachegcclean"><!-- --></a><h2 class="topictitle2">CacheGcClean</h2>
<div>
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="void" border="0" rules="none"><tbody><tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Module">Module</a></strong>: mod_disk_cache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Syntax">Syntax</a></strong>: CacheGcClean <var class="varname">hash-key-criteria
period</var></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Default">Default</a></strong>: CacheGcClean *2592000 (seconds, or 30 days)</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Context">Context</a></strong>: server config, virtual host </td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Override">Override</a></strong>: none</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Origin">Origin</a></strong>: iSeries™</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__UsageConsiderations">Usage Considerations</a></strong>: A LoadModule is required in
the configuration file prior to using the directive. The statement should
be as follows: <samp class="codeph">LoadModule disk_cache_module /QSYS.LIB/QHTTPSVR.LIB/QZSRCORE.SRVPGM</samp></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Example">Example</a></strong>: CacheGcClean http://www.ibm.com /* 1296000</td>
</tr>
</tbody>
</table>
</div>
<p> The CacheGcClean directive specifies a complete URL or URL match expression
and a maximum period value used to identify and remove data from cache that
has not been updated (or written to cache) within the number of specified
seconds. Multiple CacheGcClean directives are allowed. If disk cache maintenance
is disabled, this setting has no affect and the cache may grow without bound,
unless managed by some application or process other than the server.</p>
<p>This directive is similar to the CacheGcUnused directive, however the former
distinguishes when data was last written (or saved) to cache, not when it
was last served from cache.</p>
<blockquote><dl><dt class="dlterm"><strong>Parameter One</strong>: <em> hash-key-criteria</em></dt>
<dd><ul><li> The <var class="varname">hash-key-criteria</var> parameter accepts a complete
URL or URL match expression used to identify cached data by hash key. Complete
URLs do not contain asterisks (*) or question marks (?) and must match hash
keys URLs completely (see example two). URL match expressions contain one
or more asterisks (*) or question marks (?) used as wildcards to match multiple
hash keys. For example: <samp class="codeph">http://ibm.com/*</samp>, <samp class="codeph">*://ibm.com/*</samp>,
or <samp class="codeph">ftp://server?.ibm.com/*</samp> (see example one).</li>
</ul>
</dd>
</dl>
<dl><dt class="dlterm"><strong>Parameter Two</strong>: <em>period</em></dt>
<dd><ul><li> The <var class="varname">period</var> parameter specifies the maximum amount
of time (in seconds) that matched data may remain cached.</li>
</ul>
</dd>
</dl>
<p>Cached data for the disk caching function is identified
by comparing hash keys with the value specified for the hash-key-criteria
parameter. Matched data that has not been updated (or written to cache) within
the number of seconds specified by the corresponding period parameter is discarded
by the server during phase one of the disk cache maintenance process. Matched
data that has been updated within the number of specified seconds is not affected.
Unmatched data is not affected. See <a href="#rzaiemod_disk_cache__twodiscmain">Two Phase Disk Cache Maintenance</a> for details concerning the disk cache maintenance process. </p>
<dl><dt class="dlterm"><strong>Example 1</strong>: URL match expressions</dt>
<dd><pre> CacheRoot serverCache
CacheGcClean *://ibm.com/* 2592000
CacheGcClean ftp://server?.ibm.com/* 1209600 </pre>
<p>For this example,
the first CacheGcClean directive ensures cached data with hash keys (or URLs)
that match the expression <samp class="codeph">*://ibm.com/*</samp> and has not been
updated within the past 2592000 seconds (or 30 days) is discarded during
phase one of the cache maintenance process. The second CacheGcClean directive
ensures cached data with hash keys (or URLs) that match the expression <samp class="codeph">ftp://server?.ibm.com/*</samp> and
has not been updated within the past 1209600 seconds (or 2 weeks) is discarded.</p>
<p>Example
one uses CacheGcClean directives with URL match expressions to manage data
stored in cached using the disk cache function (CacheRoot serverCache). For
the expression <samp class="codeph">*://ibm.com/*</samp>, the first wildcard (*) is used
to match one or more characters in hash keys preceding the characters <samp class="codeph">//ibm.com/</samp>.
The second wildcard (*) is used to match one or more characters succeeding
the characters <samp class="codeph">//ibm.com/</samp>. Hash keys that match this expression,
for example, include http://ibm.com/public/welcome.html and ftp://ibm.com/patch.zip.
For the expression <samp class="codeph">ftp://server?.ibm.com/*</samp>, the first wildcard
(?) is used to match any single character between ftp://server and .ibm.com/.
The second wildcard (*) is used to match one or more characters succeeding
the characters .ibm.com/. Hash keys that match this expression, for example,
include ftp://server1.ibm.com/whitepaper.pdf and ftp://server5.ibm.com/downloads/driver.exe.</p>
</dd>
</dl>
<dl><dt class="dlterm"><strong>Example Two</strong>: Complete URL</dt>
<dd><pre> CacheRoot serverCache
CacheGcClean ftp://server5.ibm.com/downloads/application.zip 432000</pre>
<p>For
this example, the CacheGcClean directive uses a complete URL to ensure cached
data with the hash key <samp class="codeph">ftp://server5.ibm.com/downloads/application.zip</samp> is
discarded during phase one of the disk cache maintenance process if it has
not been updated within the past 432000 seconds (or 5 days). No other data
will be matched since complete URLs identify a single hash key. </p>
<p>The
server detects updates to cached data for the disk caching function by comparing
the "Data change date/time" values of data file attributes. These are commonly
referred to as last-modified times. When data is updated within cache, the
corresponding last-modified times record the date and time that the last update
was made.</p>
</dd>
</dl>
</blockquote>
<ul><li>This directive is negated when off is specified for CacheGcDaily and CacheGcInterval
is not specified.</li>
<li>This directive is used only if CacheRoot is set.</li>
<li>Disk cache maintenance may occur at regular time periods for CacheGcInterval
and at a particular time of day for CacheGcDaily if both are set.</li>
</ul>
<div class="note"><span class="notetitle">Note:</span> HTTP Server (powered by Apache) does not support inheritance for the
CacheGcClean directive.</div>
</div>
</div>
<div class="hr" id="cachegcdaily"><a name="cachegcdaily"><!-- --></a><h2 class="topictitle2">CacheGcDaily</h2>
<div>
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="void" border="0" rules="none"><tbody><tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Module">Module</a></strong>: mod_disk_cache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Syntax">Syntax</a></strong>: CacheGcDaily <var class="varname">time-of-day | off</var></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Default">Default</a></strong>: CacheGcDaily 03:00</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Context">Context</a></strong>: server config, virtual host</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Override">Override</a></strong>: none </td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Origin">Origin</a></strong>: iSeries </td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__UsageConsiderations">Usage Considerations</a></strong>: A LoadModule is required in
the configuration file prior to using the directive. The statement should
be as follows: <samp class="codeph">LoadModule disk_cache_module /QSYS.LIB/QHTTPSVR.LIB/QZSRCORE.SRVPGM</samp></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Example">Example</a></strong>: CacheGcDaily 23</td>
</tr>
</tbody>
</table>
</div>
<p> The CacheGcDaily directives specifies whether the server is to perform
disk cache maintenance, at a particular time, when the disk cache function
is enabled. If the disk cache function is disabled (the default), this setting
has no affect and the server does not perform disk cache maintenance. The
default value is 3:00 (3:00 am local system time).</p>
<blockquote><dl><dt class="dlterm"><strong>Parameter</strong>: <em>time-of-day | off</em></dt>
<dd><ul><li> The <var class="varname">time-of-day</var> parameter accepts a value in the <samp class="codeph">HH:MM:SS</samp> format
(24 hour clock) where HH is an hour value (0 to 23), MM is a minute value
(0 to 59), and SS is a second value (0 to 59). A minute (MM) or second (SS)
value is not required. If a minute value is not specified, maintenance will
commence at the beginning of the hour specified by the hour value (see example
two). Likewise, if a second value is not specified, maintenance will commence
at the specified number of minutes past the hour (see example one). </li>
<li>If <var class="varname">off</var> is specified, maintenance will not be performed
based on a particular time of day (see example three).</li>
</ul>
<p>If <var class="varname">off</var> is not specified, the server will perform
cache maintenance every day, starting at the specified local system time (if
disk caching is enabled, see examples one and two). If <var class="varname">off</var> is
specified, the server will not perform disk cache maintenance at a specific
time of day, however it may perform disk cache maintenance at regular time
intervals, if a maintenance period is set using the CacheGcInterval directive.
If <var class="varname">off</var> is specified, and a maintenance period is not specified
using CacheGcInterval, the server will never perform disk cache maintenance
(see example three).</p>
</dd>
</dl>
<dl><dt class="dlterm"><strong>Example 1</strong></dt>
<dd><pre> CacheRoot dataCache
CacheGcDaily 15:55</pre>
</dd>
</dl>
<dl><dt class="dlterm"><strong>Example 2</strong></dt>
<dd><pre>CacheRoot dataCache
CacheGcDaily 9</pre>
</dd>
</dl>
<dl><dt class="dlterm"><strong>Example 3</strong></dt>
<dd><pre>CacheRoot dataCache
CacheGcDaily off</pre>
</dd>
</dl>
<p>For example one, the server will perform cache maintenance
every day at 15:55 (or 3:55 pm local system time). For example two, the server
will perform cache maintenance every day at 9:00 (or 9:00 am local system
time). For example three, the server will not perform disk cache maintenance
since CacheGcDaily is set to off, and CacheGcInterval is not specified.</p>
</blockquote>
<p>See <a href="#rzaiemod_disk_cache__twodiscmain">Two Phase Disk Cache Maintenance</a> for
details concerning the disk cache maintenance process.</p>
<ul><li>Disk cache maintenance may occur at time intervals for CacheGcInterval
and at a particular time of day for CacheGcDaily if both are set.</li>
<li>This directive is used only if CacheRoot is set.</li>
</ul>
<div class="note"><span class="notetitle">Note:</span> HTTP Server (powered by Apache) does not support inheritance for the
CacheGcDaily directive. For the configuration shown below, garbage collection
is performed at 1:30 AM and again at 2:30 AM.</div>
<div class="note"><span class="notetitle">Example:</span> <pre>CacheRoot dataCache
CacheGcDaily 01:30:00
&lt;VirtualHost ...&gt;
CacheGcDaily 02:30 00
&lt;/Virtual Host&gt; </pre>
</div>
</div>
</div>
<div class="hr" id="cachegcinterval"><a name="cachegcinterval"><!-- --></a><h2 class="topictitle2">CacheGcInterval</h2>
<div>
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="void" border="0" rules="none"><tbody><tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Module">Module</a></strong>: mod_disk_cache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Syntax">Syntax</a></strong>: CacheGcInterval <var class="varname">period</var></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Default">Default</a></strong>: none</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Context">Context</a></strong>: server config, virtual host</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Override">Override</a></strong>: none</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Origin">Origin</a></strong>: Apache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__UsageConsiderations">Usage Considerations</a></strong>: A LoadModule is required in
the configuration file prior to using the directive. The statement should
be as follows: <samp class="codeph">LoadModule disk_cache_module /QSYS.LIB/QHTTPSVR.LIB/QZSRCORE.SRVPGM</samp></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Example">Example</a></strong>: CacheGcInterval 8100</td>
</tr>
</tbody>
</table>
</div>
<p> The CacheGcInterval directive specifies whether the server is to perform
disk cache maintenance, at regular time intervals, when the disk cache function
is enabled. Maintenance for this setting will commence at the time the server
is started, and repeat every number of specified seconds, until the server
is ended. If the disk cache function is disabled (the default), this setting
has no affect and the server does not perform disk cache maintenance.</p>
<blockquote><dl><dt class="dlterm"><strong>Parameter</strong>: <em>period</em></dt>
<dd><ul><li> The <var class="varname">period</var> parameter specifies a period for cache
maintenance cycles, in seconds. The value may include a decimal to indicate
fractional hours. For example, use CacheGcInterval 5400 to perform cache maintenance
every 5400 seconds (every 90 minutes).</li>
</ul>
</dd>
</dl>
<p> If this directive is not used (not specified), the server
will not perform disk cache maintenance at regular time intervals, however
it may at a particular time of day, if such a time is specified using the
CacheGcDaily directive. If this directive is not used (not specified), and
CacheGcDaily is set to <var class="varname">off</var>, the server will never perform
disk cache maintenance (see example two).</p>
<dl><dt class="dlterm"><strong>Example 1</strong></dt>
<dd><pre>CacheRoot dataCache
CacheGcInterval 9900</pre>
</dd>
</dl>
<dl><dt class="dlterm"><strong>Example 2</strong></dt>
<dd><pre>CacheRoot dataCache
CacheGcDaily offexample</pre>
</dd>
</dl>
<p>For example one, the server will perform disk cache maintenance
every 9900 seconds (every 2 hours and 45 minutes), starting from the time
the server is started. For example two, the server will not perform disk cache
maintenance since CacheGcDaily is set to off, and CacheGcInterval is not specified.</p>
</blockquote>
<p>See <a href="#rzaiemod_disk_cache__twodiscmain">Two Phase Disk Cache Maintenance</a> for
details concerning the disk cache maintenance process.</p>
<ul><li>Disk cache maintenance may start at regular time intervals for CacheGcInterval
and at a particular time of day for CacheGcDaily if both are set.</li>
<li>This directive is used only if CacheRoot is set.</li>
</ul>
<div class="note"><span class="notetitle">Note:</span> HTTP Server (powered by Apache) does not support inheritance for the
CacheGcInterval directive.</div>
</div>
</div>
<div class="hr" id="directiveName"><a name="directiveName"><!-- --></a><h2 class="topictitle2">CacheGcMemUsage</h2>
<div>
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="void" border="0" rules="none"><tbody><tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Module">Module</a></strong>: mod_disk_cache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Syntax">Syntax</a></strong>: CacheGcMemUsage <var class="varname">size</var></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Default">Default</a></strong>: CacheGcMemUsage 5000000</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Context">Context</a></strong>: server config, virtual host </td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Override">Override</a></strong>: none</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Origin">Origin</a></strong>: iSeries</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__UsageConsiderations">Usage Considerations</a></strong>: A LoadModule is required in
the configuration file prior to using the directive. The statement should
be as follows: <samp class="codeph">LoadModule disk_cache_module /QSYS.LIB/QHTTPSVR.LIB/QZSRCORE.SRVPGM</samp></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Example">Example</a></strong>: CacheGcMemUsage 3000000</td>
</tr>
</tbody>
</table>
</div>
<p>The CacheGcMemUsage directive specifies the maximum amount of system memory,
in bytes, the server is to use to collect information for phase two of the
disk cache maintenance process. See Two Phase Disk Cache Maintenance for details
concerning the disk cache maintenance process.</p>
<blockquote><dl><dt class="dlterm"><strong>Parameter</strong>: <em>size</em></dt>
<dd><ul><li> The <var class="varname">size</var> parameter specifies, in bytes, the amount
of main store memory that the server may use for phase two of the disk cache
maintenance process.</li>
</ul>
</dd>
</dl>
<p>When the amount of system memory consumed for phase two
of the disk cache maintenance process reaches the value specified for the
size parameter, the server stops collecting information for remaining data
in cache but continues to do the other tasks for phase one until finished.
If the server takes disk cache maintenance into phase two, only the information
collected in phase one is used. This will not include information for all
remaining cached data if the size parameter is not large enough.</p>
<dl><dt class="dlterm"><strong>Example</strong></dt>
<dd><pre>CacheRoot dataCache
CacheGcDaily 5:00
CacheGcMemUsage 200000</pre>
<p>For this example, the server will perform
disk cache maintenance every day at 5:00 (CacheGcDaily 5:00). During phase
one maintenance, the server records file names and expiration times for data
remaining cached, until it consumes 200000 bytes of memory (CacheGcMemUsage
200000). After this limits reached, the server continues to perform the other
phase one tasks. After all phase one tasks are complete, the server performs
phase two maintenance (if needed) using whatever information it was able to
collect in phase one.</p>
</dd>
</dl>
</blockquote>
<ul><li>This directive is negated when <var class="varname">off</var> is specified for
CacheGcDaily and CacheGcInterval is not specified.</li>
<li>Cache maintenance may occur at time intervals for CacheGcInterval and
at a particular time of day for CacheGcDaily if both are set.</li>
<li>This directive is used only if CacheRoot is set, and cache maintenance
is enabled.</li>
</ul>
<div class="note"><span class="notetitle">Note:</span> HTTP Server (powered by Apache) does not support inheritance for the
CacheGcMemUsage directive.</div>
</div>
</div>
<div class="hr" id="cachegcunused"><a name="cachegcunused"><!-- --></a><h2 class="topictitle2">CacheGcUnused</h2>
<div>
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="void" border="0" rules="none"><tbody><tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Module">Module</a></strong>: mod_disk_cache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Syntax">Syntax</a></strong>: CacheGcUnused <var class="varname">hash-key-criteria
period</var></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Default">Default</a></strong>: CacheGcUnused * 1209600 (seconds, or 2
weeks)</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Context">Context</a></strong>: server config, virtual host </td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Override">Override</a></strong>: none</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Origin">Origin</a></strong>: iSeries</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__UsageConsiderations">Usage Considerations</a></strong>: A LoadModule is required in
the configuration file prior to using the directive. The statement should
be as follows: <samp class="codeph">LoadModule disk_cache_module /QSYS.LIB/QHTTPSVR.LIB/QZSRCORE.SRVPGM</samp></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Example">Example</a></strong>: CacheGcUnused http://www.ibm.com/* 432000</td>
</tr>
</tbody>
</table>
</div>
<p> The CacheGcUnused directive specifies a complete URL or URL match expression
and a maximum period value used to identify and remove data from cache that
has not been used (or served from cache) within the number of specified seconds.
Multiple CacheGcUnused directives are allowed. If disk cache maintenance is
disabled (see <a href="#cachegcdaily">CacheGcDaily</a> or <a href="#cachegcinterval">CacheGcInterval</a>), this setting has no affect and the cache may grow without
bound, unless managed by some application or process other than the server
itself.</p>
<p>This directive is similar to the <a href="#cachegcclean">CacheGcClean</a> directive,
however the latter does not distinguish when data was last served from cache,
but rather when it was last written (or saved) to cache.</p>
<blockquote><dl><dt class="dlterm"><strong>Parameter One</strong>: <em>hash-key-criteria</em></dt>
<dd><ul><li> The <var class="varname">hash-key-criteria</var> parameter accepts a complete
URL or URL match expression used to identify cache data by hash key. Complete
URLs do not contain asterisks (*) or question marks (?) and must match hash
keys completely (see example two). URL match expressions contain one or more
asterisks (*) or question marks (?) as wildcards to match multiple hash keys.
For example, <samp class="codeph">http://*</samp> or <samp class="codeph">ftp://server?.ibm.com/*</samp> (see
example one).</li>
</ul>
</dd>
</dl>
<dl><dt class="dlterm"><strong>Parameter Two</strong>: <em>period</em></dt>
<dd><ul><li> The <var class="varname">period</var> parameter specifies the maximum amount
of time (in seconds) that matched data may remain cached.</li>
</ul>
</dd>
</dl>
<p>Cached data for the disk caching function is identified
for this setting by comparing hash keys with the value specified for the hash-key-criteria
parameter. Matched data that has not been used (or served from cache) within
the number of seconds specified by the corresponding period parameter are
discarded by the server during phase one of the disk cache maintenance process.
Matched data that has been used within the number of specified seconds is
not affected. Unmatched documents are not affected. See <a href="#rzaiemod_disk_cache__twodiscmain">Two Phase Disk Cache Maintenance</a> for details concerning the disk cache maintenance process.</p>
<dl><dt class="dlterm"><strong>Example 1</strong>: URL match expressions</dt>
<dd><pre>CacheRoot serverCache
CacheGcUnused http://* 25929000
CacheGcUnused ftp://server?.ibm.com/* 1209600</pre>
<p> For this example,
the first CacheGcUnused directive ensures that cached data with hash keys
(or URLs) that match the expression <samp class="codeph">http://*</samp> and has not
been updated within the past 25929000 seconds (or 30 days) are discarded during
phase one of the disk cache maintenance process. The second CacheGcClean directive
ensures that cached data with hash keys (or URLs) that match the expression <samp class="codeph">ftp://server?.ibm.com/*</samp> and
has not been updated within the past 1209600 seconds (or 2 weeks) is discarded.
</p>
<p>Example one uses CacheGcUnused directives with URL match expressions
to manage data stored in cache using the disk caching function (CacheRoot
serverCache). For the expression <samp class="codeph">http://*</samp>, the wildcard (*)
is used to match one or more characters in hash keys preceding the characters
http://. This expression matches all hash keys starting with the characters <samp class="codeph">http://</samp>.
For the expression <samp class="codeph">ftp://server?.ibm.com/*</samp>, the first wildcard
(?) is used to match any single character in hash keys between <samp class="codeph">ftp://server
and .ibm.com/</samp>. The second wildcard (*) is used to match one or more
characters in hash keys succeeding the characters .ibm.com/. Hash keys that
match this expression, for example, include <sup>ftp://server1.ibm.com/whitepaper.pdf</sup> and <samp class="codeph">ftp://server5.ibm.com/downloads/driver.exe</samp>. </p>
</dd>
</dl>
<dl><dt class="dlterm"><strong>Example 2</strong>: Complete URL</dt>
<dd><pre>ProxyRequests on
CacheRoot serverCache
CacheGcUnused ftp://server5.ibm.com/downloads/application.zip 432000</pre>
<p>For
this example, the CacheGcUnused directive uses a complete URL to ensure cached
data with the hash key <samp class="codeph">ftp://ftpserver.ibm.com/downloads/application.zip</samp> is
discarded during phase one of the disk cache maintenance process if it has
not been requested within the past 432000 seconds (or 5 days). No other data
will be matched since complete URLs identify a single hash key. </p>
<p>The
server detects requests for cached data for the disk caching function by comparing
the "Last access date/time" values of data file attributes. These are commonly
referred to as last-accessed times. When data is served from cache, the corresponding
last-accessed times record the date and time that the last request was served.</p>
</dd>
</dl>
</blockquote>
<ul><li>This directive is negated when off is specified for CacheGcDaily and CacheGcInterval
is not specified.</li>
<li>Cache maintenance may occur at regular time periods for CacheGcInterval
and at a particular time of day for CacheGcDaily if both are set.</li>
<li>This directive is used only if CacheRoot is set.</li>
</ul>
<div class="note"><span class="notetitle">Note:</span> HTTP Server (powered by Apache) does not support inheritance for the
CacheGcUnused directive.</div>
</div>
</div>
<div class="hr" id="cacheroot"><a name="cacheroot"><!-- --></a><h2 class="topictitle2">CacheRoot</h2>
<div>
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="void" border="0" rules="none"><tbody><tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Module">Module</a></strong>: mod_disk_cache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Syntax">Syntax</a></strong>: CacheRoot <var class="varname">directory</var></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Default">Default</a></strong>: none</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Context">Context</a></strong>: server config, virtual host </td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Override">Override</a></strong>: none</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Origin">Origin</a></strong>: Apache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__UsageConsiderations">Usage Considerations</a></strong>: A LoadModule is required in
the configuration file prior to using the directive. The statement should
be as follows: <samp class="codeph">LoadModule disk_cache_module /QSYS.LIB/QHTTPSVR.LIB/QZSRCORE.SRVPGM</samp></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Example">Example</a></strong>: CacheRoot webProxyCache</td>
</tr>
</tbody>
</table>
</div>
<p>The CacheRoot directive enables the disk cache function and specifies the
name of the file system directory root. Setting this directive also enables
disk cache maintenance for the CacheGcDaily directive, by default, and the
CacheGcInterval directive. See the <a href="#cachegcdaily">CacheGcDaily</a> or <a href="#cachegcinterval">CacheGcInterval</a> directives for more details on
disk cache maintenance.</p>
<blockquote><dl><dt class="dlterm"><strong>Parameter</strong>: <em>directory</em></dt>
<dd><ul><li>The <var class="varname">directory</var> parameter accepts a file system path
name to specify the file system directory root for the disk cache function
(see directory root limits below).</li>
</ul>
</dd>
</dl>
<p>The disk cache function provides underlying cache support
for a local proxy cache and user written modules, using local file system
space (disk space). The server must have *RWX data authorities and *ALL object
authorities to the specified directory. </p>
<p>A hash algorithm is used to
generate unique and seemingly random path names based on hash keys (or URLs)
provided for data stored in cache (see CacheDirLength and CacheDirLevels).
Data is stored in the local file system using these path names, relative to
the specified directory root. Since the algorithm generates case sensitive
path names, CacheRoot must specify a directory within the QOpenSys (case sensitive)
file system. For this reason the following limits are placed on the directory
root:</p>
<dl><dt class="dlterm">Directory root limits:</dt>
<dd><ul><li>If the directory parameter specifies an absolute path it must start with
/QOpenSys/QIBM/UserData/HTTPA/CacheRoot, otherwise the proxy will fail to
activate at startup.</li>
<li>If the directory parameter does not specify an absolute path (does not
start with a '/'), it will be assumed to be relative to the following: /QOpenSys/QIBM/UserData/HTTPA/CacheRoot</li>
</ul>
<p>The directory will be created if it does not exist prior to server
startup. Only the last directory in the path will be created. All other directories
in the path must previously exist. For example, if "CacheRoot abc/def" is
configured, the server will create directory "/QOpenSys/QIBM/UserData/HTTPA/CacheRoot/ABC/def".</p>
<div class="note"><span class="notetitle">Example 1:</span> Absolute Path<pre>CacheRoot /QOpenSys/QIBM/UserData/HTTPA/CacheRoot/proxyCache
ProxyRequests on</pre>
</div>
<div class="note"><span class="notetitle">Example 2:</span> Relative
Path<pre>CacheRoot proxyCache
ProxyRequests on</pre>
</div>
<div class="note"><span class="notetitle">Example 3:</span> Relative
Path (with disk cache function unavailable for proxy data)<pre>CacheRoot cache
ProxyRequests on</pre>
</div>
<div class="note"><span class="notetitle">Example 4:</span> Bad
Path<pre>CacheRoot /MyServerCache</pre>
</div>
</dd>
</dl>
<p>For example one, CacheRoot enables the disk cache function
(CacheRoot /QOpenSys/QIBM/UserData/HTTPA/CacheRoot/proxyCache) , ProxyRequests
specifies that the proxy function is enabled to handle forward proxy requests
(ProxyRequests on). With these directive settings, HTTP proxy response data
is cached and maintained within the /QOpenSys/QIBM/UserData/HTTPA/CacheRoot/proxyCache
directory using disk cache function support. See the ProxyRequests directive
for more information on handling proxy requests and caching HTTP proxy response
data. </p>
<p>For example two, the disk cache function is enabled (CacheRoot
proxyCache), the proxy function is enabled (ProxyRequests on), and the local
proxy cache is enabled. With these directive settings, HTTP proxy response
data is cached and maintained within the proxyCache directory, relative to
the /QOpenSys/QIBM/UserData/HTTPA/CacheRoot/ directory. This directory is
the same one described in example one, simply specified as a relative path
name rather than an absolute path name. Either specification is acceptable.
</p>
<p>For example three, the disk cache function is enabled (CacheRoot cache),
and the proxy function is enabled (ProxyRequests on), however the local proxy
cache is disabled. With these directive settings, the disk cache function
is not used to cache data for the proxy function, but may be used to cache
data for user written modules. </p>
<p>For example four, the directory specified
for CacheRoot is not valid since an absolute path within /QOpenSys/QIBM/UserData/HTTPA/CacheRoot/
is not specified. With this configuration the server will generate an error
message(s) at startup and fail to activate.</p>
</blockquote>
<ul><li>This directive is required when ProxyNoConnect is set to on.</li>
</ul>
<div class="note"><span class="notetitle">Note:</span> HTTP Server (powered by Apache) does not support inheritance for the
CacheRoot directive.</div>
</div>
</div>
<div class="hr" id="cachesize"><a name="cachesize"><!-- --></a><h2 class="topictitle2">CacheSize</h2>
<div>
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="void" border="0" rules="none"><tbody><tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Module">Module</a></strong>: mod_disk_cache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Syntax">Syntax</a></strong>: CacheSize <var class="varname">size</var></td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Default">Default</a></strong>: CacheSize 1000000</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Context">Context</a></strong>: server config, virtual host</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Override">Override</a></strong>: none</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Origin">Origin</a></strong>: Apache</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__UsageConsiderations">Usage Considerations</a></strong>: A LoadModule is required in
the configuration file prior to using the directive. The statement should
be as follows:<pre>LoadModule cache_module /QSYS.LIB/QHTTPSVR.LIB/QZSRCORE.SRVPGM
LoadModule disk_cache_module /QSYS.LIB/QHTTPSVR.LIB/QZSRCORE.SRVPGM</pre>
</td>
</tr>
<tr><td colspan="2" valign="top"><strong><a href="rzaiedirective-dict.htm#rzaiedirective-dict__Example">Example</a></strong>: CacheSize 8550</td>
</tr>
</tbody>
</table>
</div>
<p> The CacheSize directive specifies the maximum amount of system storage
space allocated for the disk cache function (in kilobytes). Although actual
usage may exceed this setting, the server will discard data when it runs disk
cache maintenance until the total allocated cache space is at or below this
setting. If disk cache maintenance is disabled, this setting has no affect
and the cache may grow without bound, unless managed by some application or
process other than the server itself. See <a href="#cachegcdaily">CacheGcDaily</a> or <a href="#cachegcinterval">CacheGcInterval</a> for more details on the disk
cache maintenance process.</p>
<blockquote><dl><dt class="dlterm"><strong>Parameter</strong>: <em>size</em></dt>
<dd><ul><li> The <var class="varname">size</var> parameter specifies the maximum number of
kilobytes allocated for the disk cache function. Depending on the expected
server traffic volume, and values set for CacheGcInterval or CacheGcDaily,
use a size value that is at least twenty to forty percent lower than the available
space.</li>
</ul>
</dd>
</dl>
</blockquote>
<p>The disk cache function uses the local file system to store data. Therefore,
space allocated for this cache is used to maintain directory structures and
file attributes as well as to store cache data. It also includes unused space
within file system storage blocks allocated to files and directories. Therefore,
the total amount of system storage allocated for the cache will always be
greater than the total amount of actual cache data. This setting sets a limit
for the total amount of allocated space, not a limit for the total amount
of actual cache data.</p>
<ul><li>This directive is negated when off is specified for CacheGcDaily and CacheGcInterval
is not specified.</li>
<li>This directive is used only if CacheRoot is set.</li>
</ul>
<div class="note"><span class="notetitle">Note:</span> HTTP Server (powered by Apache) does not support inheritance for the
CacheSize directive.</div>
</div>
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