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# Rules: SQLite

Last updated 29 October 2026

Check these rules before you change SQLite settings or point another tool at a database: each keeps the database working with Tonbo.

The examples use the connection `open()` returns, a node:sqlite `DatabaseSync`, as [Connect](https://tonbo.dev/docs/databases/connect.md) opens it.

### Leave the journal mode and the page size alone

`open()` sets up WAL mode with 4 KiB pages. A transaction that leaves WAL mode, changes the page size or writes in exclusive locking mode fails with `unsupported`, and the database stays usable (see [Requirements](https://tonbo.dev/docs/databases/connect.md#requirements)).

**Do**

```js
const db = await open("notes"); // WAL mode with 4 KiB pages, already set up
```

**Don’t**

```js
db.exec("PRAGMA journal_mode = DELETE"); // fails with unsupported
db.exec("PRAGMA page_size = 8192"); // fails with unsupported
```

### Reach the data only through the connection open() returns

The files in the cache directory are not SQLite files without the package, so other tools fail with `SQLITE_NOTADB` and change nothing, and a copy they could open would never reach Tonbo. Run migrations in the app (see [Use with Drizzle](https://tonbo.dev/docs/databases/drizzle.md#migrations)), and export a plain copy for other tools (see [Export a copy](https://tonbo.dev/docs/databases/backups.md#export)).

**Do**

```js
migrate(drizzle({ client: db }), { migrationsFolder: "./drizzle" }); // in the app
db.prepare("VACUUM INTO ?").run("/exports/notes.db"); // a plain copy any tool opens
```

**Don’t**

```js
// From a shell, on the cache directory:
//   npx drizzle-kit migrate      fails with SQLITE_NOTADB
//   sqlite3 notes-cache/.../db   fails with SQLITE_NOTADB
```