public Map<byte[], List<HStoreFile>> close() throws IOException {
    return close(false);
  }
Close down this HRegion. Flush the cache, shut down each HStore, don't service any more calls.
<p>
This method could take some time to execute, so don't call it from a time-sensitive thread.
@return Vector of all the storage files that the HRegion's component HStores make use of. It's
        a list of all StoreFile objects. Returns empty vector if already closed and null if
        judged that it should not close.
@throws IOException              e
@throws DroppedSnapshotException Thrown when replay of wal is required because a Snapshot was
                                 not properly persisted. The region is put in closing mode, and
                                 the caller MUST abort after this.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java