rocksdb::Status ClosePDS( const rocksdb::Slice &aPDSId )
  {
    // we currently ignore the pdsid because we don't use separate file per PDS. This might change later!!

    rocksdb::FlushOptions flOpts = rocksdb::FlushOptions();
    rocksdb::Status rs = mPDSDBHndl->Flush( flOpts );
    if( rs.ok() )
      rs = mDataDBHndl->Flush( flOpts );
    return rs;
  }