### Eclipse Workspace Patch 1.0
#P apache-trunk
Index: src/docbkx/book.xml
===================================================================
--- src/docbkx/book.xml (revision 1460946)
+++ src/docbkx/book.xml (working copy)
@@ -2175,6 +2175,28 @@
+
+
+ Online Region Merges
+
+ Both Master and Regionserver participate in the event of online region merges.
+ Client sends merge RPC to master, then master moves the regions together to the
+ same regionserver where the more heavily loaded region resided, finally master
+ send merge request to this regionserver and regionserver run the region merges.
+ Similar with process of region splits, region merges run as a local transaction
+ on the regionserver, offlines the regions and then merges two regions on the file
+ system, atomically delete merging regions from META and add merged region to the META,
+ opens merged region on the regionserver and reports the merge to Master at last.
+
+ An example of region merges in the hbase shell
+ $ hbase> merge_region 'ENCODED_REGIONNAME', 'ENCODED_REGIONNAME'
+ hbase> merge_region 'ENCODED_REGIONNAME', 'ENCODED_REGIONNAME', true
+
+ It's an asynchronous operation and call returns immediately without waiting merge completed.
+ Passing 'true' as the optional third parameter will force a merge ('force' merges regardless
+ else merge will fail unless passed adjacent regions. 'force' is for expert use only)
+
+