private void updateMetaForMergedRegions(final MasterProcedureEnv env) throws IOException {
    env.getAssignmentManager().markRegionAsMerged(mergedRegion, getServerName(env),
      this.regionsToMerge);
  }
Add merged region to META and delete original regions.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/MergeTableRegionsProcedure.java