question: public void takeSnapshot ( String tag , String ... keyspaceNames ) throws IOException { if ( operationMode == Mode . JOINING ) throw new IOException ( "Cannot snapshot until bootstrap completes" ) ; if ( tag == null || tag . equals ( "" ) ) throw new IOException ( "You must supply a snapshot name." ) ; Iterable < Keyspace > keyspaces ; if ( keyspaceNames . length == 0 ) { keyspaces = Keyspace . all ( ) ; } else { ArrayList < Keyspace > t = new ArrayList < > ( keyspaceNames . length ) ; for ( String keyspaceName : keyspaceNames ) t . add ( getValidKeyspace ( keyspaceName ) ) ; keyspaces = t ; } for ( Keyspace keyspace : keyspaces ) if ( keyspace . snapshotExists ( tag ) ) throw new IOException ( "Snapshot " + tag + " already exists." ) ; for ( Keyspace keyspace : keyspaces ) keyspace . snapshot ( tag , null ) ; }
target:  Takes the snapshot for the given keyspaces. A snapshot name must be specified.