The activateRegion()/inactivateRegion() API can be used in conjunction with a CacheLoader as well, but only if the cache loader implementation implements interface org.jboss.cache.loader.ExtendedCacheLoader. This is a subinterface of the normal CacheLoader interface. It additionally specifies the following methods needed to support the partial state transfer that occurs when a region is activated:

   /**
    * Fetch a portion of the state for this cache from secondary storage
    * (disk, DB) and return it as a byte buffer.
    * This is for activation of a portion of new cache from a remote cache.
    * The new cache would then call {@link #storeState(byte[], Fqn)}.
    *
    * @param subtree Fqn naming the root (i.e. highest level parent) node of
    *                the subtree for which state is requested.
    *
    * @see org.jboss.cache.TreeCache#activateRegion(String)
    */
   byte[] loadState(Fqn subtree) throws Exception;

   /**
    * Store the given portion of the cache tree's state in secondary storage.
    * Overwrite whatever is currently in secondary storage.
    *
    * @param state   the state to store
    * @param subtree Fqn naming the root (i.e. highest level parent) node of
    *                the subtree included in state.
    */
   void storeState(byte[] state, Fqn subtree) throws Exception;

   /**
    * Sets the RegionManager this object should use to manage
    * marshalling/unmarshalling of different regions using different
    * classloaders.
    * 
    * NOTE: This method is only intended to be used
    * by the TreeCache instance this cache loader is
    * associated with.
    * 
    *
    * @param manager the region manager to use, or null.
    */
   void setRegionManager(RegionManager manager);
 

JBossCache currently comes with two implementations of ExtendedCacheLoader, FileExtendedCacheLoader and JDBCExtendedCacheLoader. These classes extend FileCacheLoader and JDBCCacheLoader, respectively, implementing the extra methods in the extended interface.