anchor.diff:    <dir>/tomcat_home/content/thredds/cache/agg/</dir>
     <scour>24 hours</scour>
     <maxAge>90 days</maxAge>
  +  <cachePathPolicy>nestedDirectory</cachePathPolicy>
   </AggregationCache>
   ----------------------------------------------------
   
  
positive.code: change, set *scour* to ``-1'' to disable the operation. Otherwise, make
  *maxAge* longer than the longest time between changes. Basically, you
  don’t want to remove active aggregations.
  
  This cache information is intended to be permanent; it stores coordinate
  information from each file in the aggregation, so that the file does not
  
negative.code: Write permission will be determined by what rights the _Tomcat user_ has
  (the user that starts up Tomcat). For security reasons, you want to
  carefully limit the file permissions of the Tomcat user.
  
  2.  The policy must be set to one of _oneDirectory_ or _nestedDirectory_
  (the default). _oneDirectory_ will put all index files into the same
  directory, while _nestedDirectory_ will preserve the directory structure
  of the index files. Use _nestedDirectory_ for large collections of
  files, as some file systems struggle when a directory contains thousands
  of files.
  
  3.  Every *scour* amount of time, any files in the cache that are older
  than *maxAge* will be removed. To turn off scouring, set the scour time
  to 0 (eg ``0 hours''), or leave out the <scour> element. Typically you
  