GlobalTransaction getGlobalTransaction() throws SystemException {
    Transaction txn = getTransaction();
    if (txn == null) {
      return null;
    }
    GlobalTransaction gtx = (GlobalTransaction) globalTransactionMap.get(txn);
    return gtx;
  }
Get the Global Transaction associated with the calling thread
geode-core/src/main/java/org/apache/geode/internal/jta/TransactionManagerImpl.java