[Cassandra Wiki] Update of "FAQ" by gdusbabek

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The "FAQ" page has been changed by gdusbabek.
The comment on this change is: FAQ entry to indicate batch_mutate is not atomic..
http://wiki.apache.org/cassandra/FAQ?action=diff&rev1=71&rev2=72

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   * [[#gui|Is there a GUI admin tool for Cassandra?]]
   * [[#a_long_is_exactly_8_bytes|Insert operation throws InvalidRequestException with message "A long is exactly 8 bytes"]]
   * [[#clustername_mismatch|Cassandra says "ClusterName mismatch: oldClusterName != newClusterName" and refuses to start]]
+  * [[#batch_mutate_atomic|Are batch_mutate operations atomic?]]
  
  <<Anchor(cant_listen_on_ip_any)>>
  
@@ -288, +289 @@

  
  To prevent operator errors, Cassandra stores the name of the cluster in its system table.  If you need to rename a cluster for some reason, it is safe to remove system/LocationInfo* after forcing a compaction on all ColumnFamilies (with the old cluster name) if you've specified the node's token in the config file, or if you don't care about preserving the node's token (for instance in single node clusters.)
  
+ <<Anchor(batch_mutate_atomic)>>
+ == Are batch_mutate operations atomic? ==
+ 
+ No.  [[API#batch_mutate|batch_mutate]] is a way to group many operations into a single call in order to save on the cost of network round-trips.  If `batch_mutate` fails in the middle of its list of mutations, no rollback occurs and the mutations that have already been applied stay applied. 
+