---
title: "Migration"
description: "a change to a schema, forward only, re-declaring the list of applied migrations"
section: concepts
address: /concepts/migration
contract: 0476e35e6e275db5
---

# Migration

a change to a schema, forward only, re-declaring the list of applied migrations

[figure: Migration is a definition at platform scope. The drawing shows its fields and the objects that they point at.]

| property | value |
|---|---|
| kind | definition |
| scope | platform |
| key | its number |
| store | postgres |
| family | releases |



## Fields


| field | type | required | note |
|---|---|---|---|
| `number` | `count` | yes |  |
| `applies_to` | `text` | yes |  |
| `declared_list` | `[count]` | yes |  |
| `allows_rollback` | `bool` | yes |  |



## Routes that use it
No route takes or returns Migration directly. The record holds it, and the objects that point at it reach it.