docs: public static void rcvXARollback(CommsByteBuffer request,
                                      Conversation conversation,
                                      int requestNumber,
                                      boolean allocatedFromBufferPool,
                                      boolean partOfExchange)
     {
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(tc, "rcvXARollback",
                                             new Object[]
                                             {
                                                request,
                                                conversation,
                                                ""+requestNumber,
                                                ""+allocatedFromBufferPool,
                                                ""+partOfExchange
                                              });
  
        ConversationState convState = (ConversationState) conversation.getAttachment();
        ServerLinkLevelState linkState = (ServerLinkLevelState) conversation.getLinkLevelAttachment();
  
        final boolean optimizedTx = CommsUtils.requiresOptimizedTransaction(conversation);
  
        try
        {
           int clientTransactionId = request.getInt();
           if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled())
           {
              SibTr.debug(tc, "XAResource Object ID", clientTransactionId);
           }
  
           if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) SibTr.debug(tc, "Getting Xid");
           XidProxy xid = (XidProxy) request.getXid();
           if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) SibTr.debug(tc, "Completed:", xid);
  
           boolean endRequired = false;
           int endFlags = 0;
           if (optimizedTx)
           {
              endRequired = request.get() == 0x01;
              endFlags = request.getInt();
  
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled())
              {
                 SibTr.debug(tc, "End Required:", ""+endRequired);
                 SibTr.debug(tc, "End Flags:", ""+endFlags);
              }
           }
  
           boolean requiresMSResource = false;
           if (conversation.getHandshakeProperties().getFapLevel() >= JFapChannelConstants.FAP_VERSION_5)
           {
              requiresMSResource = request.get() == 0x01;
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) SibTr.debug(tc, "Requires MS Resource:", ""+requiresMSResource);
           }
  
           // Get the transaction out of the table
           IdToTransactionTable transactionTable = linkState.getTransactionTable();
           if (endRequired) transactionTable.endOptimizedGlobalTransactionBranch(clientTransactionId, endFlags);
  
           // Update transaction table atomically as receive listener dispatcher may dispatch
           // rollback (or commit + rollback) requests concurrently.
           SITransaction tran = null;
           synchronized(transactionTable)
           {
              tran = transactionTable.getResourceForGlobalTransactionBranch(clientTransactionId, xid);
              if (tran != null)
              {
                 transactionTable.removeGlobalTransactionBranch(clientTransactionId, xid);
              }
           }
  
           if (tran != IdToTransactionTable.INVALID_TRANSACTION)
           {
              // Get the actual transaction ...
              SIXAResource xaResource = getResourceFromTran(tran, convState, requiresMSResource);
  
              // Now call the method on the XA resource
              xaResource.rollback(xid);
           }
  
           try
           {
              conversation.send(poolManager.allocate(),
                                JFapChannelConstants.SEG_XAROLLBACK_R,
                                requestNumber,
                                JFapChannelConstants.PRIORITY_MEDIUM,
                                true,
                                ThrottlingPolicy.BLOCK_THREAD,
                                null);
           }
           catch (SIException e)
           {
              FFDCFilter.processException(e,
                                          CLASS_NAME + ".rcvXARollback",
                                          CommsConstants.STATICCATXATRANSACTION_XAROLLBACK_01);
  
              SibTr.error(tc, "COMMUNICATION_ERROR_SICO2027", e);
           }
        }
        catch (XAException e)
        {
           FFDCFilter.processException(e,
                                       CLASS_NAME + ".rcvXARollback",
                                       CommsConstants.STATICCATXATRANSACTION_XAROLLBACK_02);
  
           if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) SibTr.debug(tc, "XAException - RC: " + e.errorCode, e);
  
           StaticCATHelper.sendExceptionToClient(e,
                                                 CommsConstants.STATICCATXATRANSACTION_XAROLLBACK_02,
                                                 conversation, requestNumber);
        }
  
        request.release(allocatedFromBufferPool);
  
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(tc, "rcvXARollback");
     }