# Settings

Settings apply at three scopes. Choose the scope according to whether a value should configure the service, persist with a database or affect one format operation.

## Scopes

| Scope            | Interface                                | Lifetime                                                                |
| ---------------- | ---------------------------------------- | ----------------------------------------------------------------------- |
| Server           | XML configuration                        | Applied at startup; changes require restart.                            |
| Database         | SET or a documented PRAGMA/catalog write | Persisted with the selected database and applied before later requests. |
| Format statement | SETTINGS clause                          | Applies only to that statement.                                         |

`foreign_keys`, `recursive_triggers`, `user_version` and `application_id` use PRAGMA or validated `system.settings` writes rather than SET.

Database management changes require autocommit and no active transactions in the selected database. Resource limits are sampled once per request, so a SET within a batch changes defaults for later requests.

## Inspecting values

SHOW SETTINGS and `system.settings` report effective database values and read-only format defaults. Server-only XML options are not listed there. Read `main.settings` when the stored database value is required instead of its effective value.

## Ceilings

A nonzero server resource limit is a ceiling. A larger saved database value, or a saved zero meaning no database limit, cannot bypass it. A smaller nonzero database value tightens the ceiling.

See [database settings](https://coordinatordb.com/docs/reference/settings/session-settings), [format settings](https://coordinatordb.com/docs/reference/settings/formats) and [server ceilings](https://coordinatordb.com/docs/concepts/features/configuration/settings/constraints-on-settings).