# External

`external` is a list of snapshot paths, one file per owning catalog. Omitted means this project owns every table it declares.

Each path is what `okm catalog export` wrote. `okm check` and `okm migrate check` compare every `external()` table with those files. A missing file, a table the files do not list, or columns that differ is OKM1841. When a target is selected, the same commands also compare the file with that database.

```ts title="okmodel.config.ts"
import { defineConfig } from "okmodel/migrate";

export default defineConfig({
  schema: "./schema.ts",
  database: process.env.DATABASE_URL!,
  namespace: "billing",
  external: ["../identity/identity.okm.json"], // [!code focus]
});
```

The declaration is [Several catalogs](/docs/define/schema/catalogs).