code: @Override
      public byte[] getGlobalId() {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              Tr.entry(tc, "getGlobalId");
  
          byte[] globalId = null;
  
          final TransactionImpl tran = ((TranManagerSet) TransactionManagerFactory.getTransactionManager()).getTransactionImpl();
  
          if (tran != null) {
              globalId = tran.getTID();
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              Tr.exit(tc, "getGlobalId", globalId);
          return globalId;
      }
docs: Returns the <code>CosTransactions::PropagationContext::TransIdentity::tid</code> for
  the transaction currently associated with the calling thread.
  
  @return the current transaction <code>tid</code> in the form of a byte array.
  If there is no active transaction currently associated with the thread,
  return null;