public void writeBackupStartCode(Long startCode, String backupRoot) throws IOException {
    if (LOG.isTraceEnabled()) {
      LOG.trace("write backup start code to backup system table " + startCode);
    }
    try (Table table = connection.getTable(tableName)) {
      Put put = createPutForStartCode(startCode.toString(), backupRoot);
      table.put(put);
    }
  }
Write the start code (timestamp) to backup system table. If passed in null, then write 0 byte.
@param startCode  start code
@param backupRoot root directory path to backup
@throws IOException exception
hbase-backup/src/main/java/org/apache/hadoop/hbase/backup/impl/BackupSystemTable.java