Data migration
Also called: Migration
Code that converts data saved by an older app version into the format a newer version expects.
Definition
When an app changes how it stores data, every older format must be converted on update. Migrations that only handle the previous version break for users who skip versions.
In practice
Users who update from 1.0 straight to 2.0 lose their favorites because only the 1.9 → 2.0 migration exists.