# `PhoenixMountable.MigrationError`
[🔗](https://github.com/hattoriai/phoenix_mountable/blob/v0.2.1/lib/phoenix_mountable/migrations/errors.ex#L10)

Raised when a library's migration cannot run in the database's current
state: a backfill it needs has not finished, it must run outside a
transaction, or a version cannot be rolled back.

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*Consult [api-reference.md](api-reference.md) for complete listing*