# Irreversible Migration

> A defect in which a schema or data change can neither run beside the old version nor be rolled back.

Record: `architecture:irreversible-migration`
Kind: anti-pattern
Layer: [Enforcement Core](https://banes-lab.com/records/layer/enforcement-core.md)
Severity: discouraged
Scope: contract_compatibility, architecture_evolution
Canonical: https://banes-lab.com/ontology#architecture-irreversible-migration

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Big-Bang Release](https://banes-lab.com/records/architecture/big-bang-release.md) and before [Big-Upfront Frozen Architecture](https://banes-lab.com/records/architecture/big-upfront-frozen-architecture.md).

## Repair

- Refactored by: expand_contract_migration, backup, dual_read_write_temporarily, rollback_test
- Detected by: drop_column_before_consumers_removed, destructive_data_transform_no_backup, no_backward_compatible_phase
- Violated by: Apply schema, data, or infrastructure changes that cannot safely run alongside old versions or be rolled back.
- Measured by: migrations without a down step or a compatible phase
- Enforced by: migration review, rollback tests

## Severity

- [discouraged](https://banes-lab.com/records/vocabulary/severity-discouraged.md)

## Category

- [Anti-patterns](https://banes-lab.com/records/architecture-category/anti-patterns.md)

## Force

- [Architecture evolution](https://banes-lab.com/records/force/architecture-evolution.md)
- [Contract compatibility](https://banes-lab.com/records/force/contract-compatibility.md)

## Negated by

- [Rollback](https://banes-lab.com/records/architecture/rollback.md)

## Linked from

- [Anti-patterns](https://banes-lab.com/ontology/principles/architecture-category-anti-patterns.md)
- [Self-Healing / Recovery / Deployment Safety](https://banes-lab.com/ontology/principles/architecture-category-self-healing-recovery-deployment-safety.md)
- [Self-Healing / Recovery / Deployment Safety](https://banes-lab.com/ontology/lexicon/lexicon-category-self-healing-recovery-deployment-safety.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The forces](https://banes-lab.com/ontology/schema/the-forces.md)