Sql Server does not allow for user defined constants. So we are forced to take other routes like hard-coded values, scalar udf's, settings tables, etc. Unfortunately, all methods are not equal. You need to carefully consider your use of different methods, and test the results as all of these methods...
As does everyone from time-to-time, we had a lovely "learn as you go" moment in the middle of a deployment recently. As it turns out there are some very specific rules for setting up MS DTC in a clustered environment. As always, individual results may very. First of all, most DTC changes don't...