Getting started with data migration
This is one of those topics that looks small until it costs you something. A short on-ramp to data migration for teams who have not touched it before.
Data outlives the applications built on top of it, which is why the model deserves more thought than the screens. If it only works because one person remembers to do something, it does not work yet.
The reason this keeps coming up
Migrations fail on the data nobody knew existed. That sounds obvious written down. It is still the thing most often skipped. The practical test is whether someone new to the project could tell, in a minute, that it had been handled.
Your first week
- Find out what is already in place
- Run it against a full copy before the real thing
- Change one thing and measure it
Always have a documented way back. In practice this is a scheduling problem more than a technical one. If two people in the business would answer this differently, that gap is the actual problem.
In practice
Numbers get quoted in meetings long after anyone remembers how they were calculated. Three things worth confirming about data migration before you move on:
- Someone can say what the current setup is without going to look
- Migrations fail on the data nobody knew existed — and you know whether that is true here
- There is a way to tell whether the last change to this helped
If any of that sounds like a description of your current setup, it is fixable.