docs: private void cleanStaleFiles(File backupDir, AsyncOperationStatus status) {
          String[] filesInEnv = env.getHome().list();
          String[] filesInBackupDir = backupDir.list();
          if(filesInEnv != null && filesInBackupDir != null) {
              HashSet<String> envFileSet = new HashSet<String>();
              for(String file: filesInEnv)
                  envFileSet.add(file);
              // delete all files in backup which are currently not in environment
              for(String file: filesInBackupDir) {
                  if(file.endsWith(BDB_EXT) && !envFileSet.contains(file)) {
                      status.setStatus("Deleting stale jdb file :" + file);
                      File staleJdbFile = new File(backupDir, file);
                      staleJdbFile.delete();
                  }
              }
          }
      }