private int validateDBE() throws IOException {
    int incompatibilities = 0;

    LOG.info("Validating Data Block Encodings");

    try (Connection connection = ConnectionFactory.createConnection(getConf());
      Admin admin = connection.getAdmin()) {
      List<TableDescriptor> tableDescriptors = admin.listTableDescriptors();
      String encoding = "";

      for (TableDescriptor td : tableDescriptors) {
        ColumnFamilyDescriptor[] columnFamilies = td.getColumnFamilies();
        for (ColumnFamilyDescriptor cfd : columnFamilies) {
          try {
            encoding = Bytes.toString(cfd.getValue(DATA_BLOCK_ENCODING));
            // IllegalArgumentException will be thrown if encoding is incompatible with 2.0
            DataBlockEncoding.valueOf(encoding);
          } catch (IllegalArgumentException e) {
            incompatibilities++;
            LOG.warn("Incompatible DataBlockEncoding for table: {}, cf: {}, encoding: {}",
              td.getTableName().getNameAsString(), cfd.getNameAsString(), encoding);
          }
        }
      }
    }

    if (incompatibilities > 0) {
      LOG.warn("There are {} column families with incompatible Data Block Encodings. Do not "
        + "upgrade until these encodings are converted to a supported one. "
        + "Check https://s.apache.org/prefixtree for instructions.", incompatibilities);
    } else {
      LOG.info("The used Data Block Encodings are compatible with HBase 2.0.");
    }

    return incompatibilities;
  }
Check DataBlockEncodings of column families are compatible.
@return number of column families with incompatible DataBlockEncoding
@throws IOException if a remote or network exception occurs
hbase-server/src/main/java/org/apache/hadoop/hbase/tool/DataBlockEncodingValidator.java