Rolling upgrades
Another thing to consider when doing database migrations is what can be referred to as rolling upgrades. These kinds of deployments are common when you don't want your end user to experience any downtime, or at least very little downtime.
Here is an example of a rolling upgrade for our organization's customer database.
When we start, we have a running system with one database and two servers. We have a load balancer in front of the two servers.
We are going to roll out a change to the database schema, which also affects the servers. We are going to split the customer name field in the database into two separate fields, first name and surname.
This is an incompatible change. How do we minimize downtime? Let's look at the solution:
We start out by doing a database migration that creates the two new name fields and then fills these new fields by taking the old name field and splitting the field into two halves by finding a space character in the name. This was the initial chosen...
