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Store migration error

Do you see this when you start Kase?


Data Loading Error

An error occurred during persistent store migration.


Instead of the normal "Box of Decks" window, you are brought into Kase's Restore Mode. Now what?

What does it mean?

The updated Kase app works with a specific version of the database files. The updated Kase app (and the underlaying Core Data framework) should migrate your existing database to the newer version but the migration failed for some reason.

Core Data's migration is usaully very reliable, but it is not perfect. Sometimes an imperfect migration leaves behind some unused bits, and subsequent migrations accumulate this kind of unused bits and they eventually could cause a migration failure.

When migration fails, your existing data is not changed -- it is still safe. However, the newer/updated Kase app cannot start anymore because it expects and only works with the matching model version.

Kase release & database model version

Kase releasedatabase model version
3.1, 3.2, 3.3v77

What to do?

Backup is fresh?

If you have a recent backup, restore from it and everything should be fine.

No recent backup?


Good news, a backup-and-restore cycle usually can repair the database.

Assume the Kase app is updated to 3.5, and the migration error happened while trying to update the model from v82 to v83.

  1. Download the previous version of Kase that can open the existing model (in this case, Kase 3.4 for model v82).
  2. When Kase successfully opens, do a backup-and-restore cycle.
    1. Backup: use Standard mode, not Files mode
    2. Restore
    3. This should repair the database issues.
  3. Re-download the lastest version of Kase (in this case, Kase 3.5 for model v83)
    • Migration should be able to complete.