code: protected void internalStart(Xid xid, int flags) throws XAException
     {
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(this, tc, "internalStart", new Object[] {xid, ""+flags});
              
        try
        {
           CommsByteBuffer request = getCommsByteBuffer();
           request.putInt(getTransactionId());
           request.putXid(xid);
           request.putInt(flags);
           if (fapLevel >= JFapChannelConstants.FAP_VERSION_5) {
              request.put((byte)(isMSResource ? 0x01 : 0x00));
           }  
           
           CommsByteBuffer reply = jfapExchange(request, 
                                                JFapChannelConstants.SEG_XASTART, 
                                                JFapChannelConstants.PRIORITY_MEDIUM, 
                                                true);
           try
           {
              reply.checkXACommandCompletionStatus(JFapChannelConstants.SEG_XASTART_R, getConversation());
           }
           finally
           {
              reply.release();
           }
        }
        catch (XAException xa)
        {
           // No FFDC Code needed
           // Simply re-throw...
           throw xa;
        }
        catch (Exception e)
        {
           FFDCFilter.processException(e, CLASS_NAME + ".internalStart",
                                       CommsConstants.SIXARESOURCEPROXY_START_01, this);
  
           if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) SibTr.debug(this, tc, "Caught a comms problem:", e);
           throw new XAException(XAException.XAER_RMFAIL);
        }
        
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(this, tc, "internalStart");
     }
docs: Called when the application wishes to mark the start of the
  unit of work in the transaction represented by this Xid.
  <p>
  Across the wire we will flow:
  <p>
  BIT32    Transaction Id
  The XID Structure
  BIT32    Flags
  
  @param xid
  
  @throws XAException if an exception is thrown at the ME. In the
  event of a comms failure, an XAException with XAER_RMFAIL will
  be thrown.