[API reference](https://evolu.dev/docs/api-reference) › [@evolu/sqlite-wasm](https://evolu.dev/docs/api-reference/sqlite-wasm) › sahPoolDigestV2Flag

```ts
const sahPoolDigestV2Flag: 128 = SQLITE_OPEN_MEMORY;
```

Defined in: [packages/sqlite-wasm/src/SahPool.ts:1292](https://github.com/evoluhq/evolu/blob/bc4578a260dd15d5bbf94b83765ca05984d194cb/packages/sqlite-wasm/src/SahPool.ts#L1292)

The flag that marks a header digest as version 2.

Opfs-sahpool before SQLite 3.50 computed every digest as `[0, 0]` because of
an overflow. The fix repurposed SQLITE_OPEN_MEMORY, which never reaches a
VFS, to mark headers written with the fixed digest, so older headers stay
valid.