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<?xml version="1.0"?>

<document>
  <properties>
    <title>Berkeley DB Disk Auxiliary Cache</title>
    <author email="ASmuts@yahoo.com">Aaron Smuts</author>
  </properties>

  <body>
    <section name="Berkeley DB Disk Auxiliary Cache">
      <p>
        The Berkeley DB Disk Auxiliary Cache is an optional plugin for the
        JCS.  It is primarily intended to provide a secondary store to
        ease the memory burden of the cache.  When the memory cache
  	    exceeds its maximum size it tells the cache hub that the item
	      to be removed from memory should be spooled to disk.  The cache
	      checks to see if any auxiliaries of type "disk" have been
	      configured for the region.  If the "Berkeley DB Disk Auxiliary Cache"
	      is used, the item will be spooled to disk.
      </p>
      <p>
		The Berkeley DB is far slower than the Indexed Disk Cache, especially for puts.
		This is partially due to the fact that the BDB store its keys on disk.
		However, any items stored in the BDB will be available on restart, even if
		the cache is not shutdown properly.
      </p>
      <p>
		The Berkeley DB requires jdk1.4 and above.  As such, it is distributed
		in the jdk14-ext jar.
      </p>

      <subsection name="Configuration">
        <p>
          The configuration is simple and is done in the auxiliary
          cache section of the <code>cache.ccf</code> configuration file.
          In the example below, I created a Berkeley DB Auxiliary Cache
          referenced by <code>BDBDC</code>.  It uses files located in the
          "DiskPath" directory.
         </p>

            <source><![CDATA[
# #############################################################
# #### Default Region Configuration
jcs.default=BDBDC
jcs.default.cacheattributes=org.apache.commons.jcs.engine.CompositeCacheAttributes
jcs.default.cacheattributes.MaxObjects=100
jcs.default.cacheattributes.MemoryCacheName=org.apache.commons.jcs.engine.memory.lru.LRUMemoryCache

# #############################################################
# #### CACHE REGIONS
jcs.region.myRegion1=BDBDC
jcs.region.myRegion1.cacheattributes=org.apache.commons.jcs.engine.CompositeCacheAttributes
jcs.region.myRegion1.cacheattributes.MaxObjects=1000
jcs.region.myRegion1.cacheattributes.MemoryCacheName=org.apache.commons.jcs.engine.memory.lru.LRUMemoryCache

# #############################################################
# #### AUXILIARY CACHES
# Berkeley DB JE
jcs.auxiliary.BDBDC=org.apache.commons.jcs.auxiliary.disk.bdbje.BDBJECacheFactory
jcs.auxiliary.BDBDC.attributes=org.apache.commons.jcs.auxiliary.disk.bdbje.BDBJECacheAttributes
jcs.auxiliary.BDBDC.attributes.DiskPath=target/
jcs.auxiliary.BDBDC.attributes.MaxPurgatorySize=100000
        ]]></source>
          </subsection>

    </section>
  </body>
</document>