Here is the scenario. Our enterprise has multiple applications where the business key value is identical in a couple of applications but doesn’t represent the same entity. The collision code is supposed to provide the tie-breaking value in the hash calculation. However, that value is not supposed to identify the application. What rules determine a valid value for the collision code in this scenario?
The collision code needs to identify the business area (east coast/west coast, Europe/US, Finance/HR) in which the business key serves as an identifier. Sometimes it is the case that the only “business area” where the business key serves as an identifier is the source-system.
Make sure you do the leg-work to ensure that number isn’t being used elsewhere, though. Does HR actually use that number inter-department when they need to employee’s contract? Maybe the collision code is HR… Or maybe whatever HR uses to identify a person doesn’t actually line up neatly to any unique identifier and the business area for the key is only within the scope of the source system. Data is messy. We tidy where we can.