List of tunable caches in the ZCS server
----------------------------------------

IndexReadersCache
=================

What:
   A cache of recently opened Lucene IndexReaders.  This short-lived
cache keeps the per-mailbox Lucene index from being closed and
re-opened multiple times during searches, or when multiple searches
are issued to the same mailbox in close proximity.
   Opening an index for reading is a fairly expensive task as it
requires the index's word dictionary to be loaded from disk.  An open
Reader requires a significant amount of server memory when open, so
increasing the cache parameters will cause the server to use more
memory.
   Setting LC.zimbra_index_reader_lru_size to "0" disables this cache.
Disabling the cache will cause a significant performance impact when
searching large indexes.
           
Owner:
   tim@zimbra.com

Tunable Parameters:
   LC.zimbra_index_reader_lru_size
      max # IndexReaders cached simultaneously in system.  
   LC.zimbra_index_reader_idle_flush_time
      time (seconds) to hold the IndexReader open before closing it.
   LC.zimbra_index_reader_idle_sweep_frequency
      frequency (seconds) to sweep the cache looking for readers to
      close.


      
IndexWritersCache
=================

What:
   When writing data to an index, Lucene performs significantly better
in "batch mode" - if it writes multiple documents to disk at one time.
The IndexWriters cache attempts to batch index writes by keeping the
most recently written-to indexes open for a while before committing
the data to disk.
   Setting the max_uncommitted_operations to "0" effectively disables
this cache, causing all index writes to be written through to disk
immediately.

Owner:
   tim@zimbra.com

Tunable Parameters:
   LC.zimbra_index_max_uncommitted_operations
      Per-Index, the maximum # uncommitted documents we store in
      memory before flushing the index to disk.  Raising this # will
      improve performance, but will raise memory pressure on the server.
   LC.zimbra_index_lru_size
      Number of index writers the server will allow to simultaneously
      be open.  
   LC.zimbra_index_idle_flush_time
      Idle timeout (seconds) to wait before flushing an open index
      writer.