code: private StreamSet getStreamSetForMessage(AbstractMessage msg) throws SIResourceException {
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
        SibTr.entry(tc, "getStreamSetForMessage", new Object[] {msg});
  
      SIBUuid12 streamID = msg.getGuaranteedStreamUUID();
      StreamSet streamSet = null;
  
      // Synchronize on the stream set while getting it, and persisting
      // any change.
      synchronized(streamSets)
      {
        streamSet = (StreamSet) streamSets.get(streamID);
        if (streamSet != null)
        {
          // We have an existing stream set.
          // We need to ensure that the destination UUID is correct, as
          // it is possible for this to change on the remote side if the
          // foreign bus (and hence virtual link UUID) is change. We must
          // send back our reply stamped with the correct destination UUID.
          SIBUuid12 msgDest = msg.getGuaranteedTargetDestinationDefinitionUUID();
          if (msgDest != null && !msgDest.equals(streamSet.getDestUuid())) {
            // Update our in-memory destination UUID on the stream set.
            // Note that we don't attempt to persist any change here.
            // The change will be persisted the next time the stream set
            // is persisted for any other reason. There is no benefit
            // to updating the persisted representation here (and doing
            // so has been seen to fail in some cases).
            streamSet.setDestUuid(msgDest);
          }
        }
      }
  
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
        SibTr.exit(tc, "getStreamSetForMessage", streamSet);
      return streamSet;
     }
docs: Get any existing stream set for the stream UUID and destination UUID
  specified in the message. If an existing destination exists with the
  correct stream UUID, but an incorrect destination UUID (due to
  recreation of the virtual link on the remote side), the stream
  set will be updated before returning to the caller.
  @return The existing stream set, with a correct dest UUID, or null