OAK-4900: Enable persistent caches by default

Update documentation

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1765557 13f79535-47bb-0310-9956-ffa450edef68

oak-doc/src/site/markdown/nodestore/persistent-cache.md

@@ -27,19 +27,17 @@ the load on the storage backend.
 
 ### OSGi Configuration
 
-The OSGi configuration of the persistent cache is:
+The default OSGi configuration of the persistent cache is:
 
     org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreService
-        persistentCache=./cache
+        persistentCache=cache,binary=0
 
-This will enable the persistent cache, and set the configuration option to "./cache".
-
-### Configuration Options 
+### Configuration Options
 
 The persistent cache configuration setting is string with a number of comma separated elements. 
 The first element is the directory where the cache is stored. Example:
 
-    ./cache
+    cache
 
 In this case, the data is stored in the directory "cache", 
 relative to the `repository.home` directory. If no repository home directory is
@@ -85,20 +83,29 @@ To disable this option, use "-compress".
 Those setting can be appended to the persistent cache configuration string.
 An example configuration is:
 
-    ./cache,size=2048,binary=0,-compact,-compress
+    cache,size=2048,binary=0,-compact,-compress
+
+To disable the persistent cache entirely, use the following configuration:
+
+    org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreService
+        persistentCache=-
 
 ### Journal cache
 
-Diff cache entries can also be stored in a separate persistent cache and
-configured independently if needed. This can be enabled in the OSGi
+Since Oak 1.6.
+
+Diff cache entries can also are stored in a separate persistent cache and
+configured independently if needed. This can be done in the OSGi
 configuration like in the following example:
 
     org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreService
-        persistentCache=./cache,size=2048
-        journalCache=./journal,size=1024
+        persistentCache=cache,size=2048
+        journalCache=diff-cache,size=1024
 
 The configuration options are the same as for the `persistentCache`, but options
-unrelated to the diff cache type are ignored.
+unrelated to the diff cache type are ignored. The default configuration is
+`journalCache=diff-cache` and can be disabled the same way as the
+regular persistent cache with a dash: `journalCache=-`.
 
 ### Dependencies
 

oak-doc/src/site/markdown/osgi_config.md

@@ -111,7 +111,7 @@ blobCacheSize
   `blobCacheSize`. 
 
 persistentCache
-: Default "" (an empty string, meaning disabled)
+: Default "cache,binary=0" (prior to 1.6, the persistent cache was disabled by default)
 : The [persistent cache][persistent-cache], which is stored in the local file system.
 
 <a name="cache-allocation"></a>