SOLR uses several Caches in order to retain some result information in memory. Since version 2.0 this this feature can be disabled in order to decrease the use of RAM memory.
From version 2.0.2, the SOLR Document Caches feature is disabled by default, including the following properties in the solrcore.properties file.
solr.documentCache.size=0 solr.documentCache.initialSize=0 solr.documentCache.autowarmCount=0
Note: This configuration will require a smaller amount of RAM memory when
searching which may help to reduce requirements and to increase performance.
When applying these flags to an existing SOLR Core, no re-indexing operation is recommended. Once the properties have been set in the solrcore.properties file, all the performance benefits will be available immediately.