public void initTxMemberId() {
    txUniqId = TXManagerImpl.getCurrentTXUniqueId();
    TXStateProxy txState = TXManagerImpl.getCurrentTXState();
    if (txState != null) {
      // [DISTTX] Lets not throw this exception for Dist Tx
      if (canStartRemoteTransaction() && txState.isRealDealLocal() && !txState.isDistTx()) {
        // logger.error("sending rmt txId even though tx is local! txState=" + txState, new
        // RuntimeException("STACK");
        throw new IllegalStateException(
            "Sending remote txId even though transaction is local. This should never happen: txState="
                + txState);
      }
      txMemberId = txState.getOriginatingMember();
    }
  }
The unique transaction Id on the sending member, used to construct a TXId on the receiving side
geode-core/src/main/java/org/apache/geode/internal/cache/partitioned/PartitionMessage.java