code: BlockInfo[] setReplication(String src,
                           short replication,
                           int[] oldReplication
                           ) throws IOException {
      waitForReady();
      BlockInfo[] fileBlocks = unprotectedSetReplication(src, replication, oldReplication);
      if (fileBlocks != null)  // log replication change
        fsImage.getEditLog().logSetReplication(src, replication);
      return fileBlocks;
    }
docs: Set file replication
  
  @param src file name
  @param replication new replication
  @param oldReplication old replication - output parameter
  @return array of file blocks
  @throws IOException