# last-backed-up-event-unknown

The database holds **no event** with the ID that **`lastBackedUpEvent`** names.

- **Route:** `create-backup`
- **Description:** `last backed up event is unknown: the store holds no event with its ID`
- **Details:** **`value`**, the ID of `lastBackedUpEvent` as the request gave it.

## Why It Happens

An increment of a **[backup](/docs/eventsourcingdb/backup-and-restore)** follows on the event the previous backup ended at. So before it sends anything, EventSourcingDB looks up the event with the ID that **`lastBackedUpEvent`** names. Here, the database **has no such event**: it holds no events at all, or its latest event has a lower ID.

Events are never removed, so this usually means that the request goes to **another database** than the one the previous backup was created from, such as a new one, or that the database was **restored from an older backup** since. If the database holds the event, but with another hash, EventSourcingDB reports **[`last-backed-up-event-mismatched`](/docs/eventsourcingdb/errors/last-backed-up-event-mismatched)** instead.

## How to Fix It

Send the request to the database the previous backup was created from. If the backups no longer fit the database, start anew with a full backup, with `lastBackedUpEvent` set to `null`. Resending the request to this database fails the same way, as long as it holds no event with that ID.

## Example

For an increment whose `lastBackedUpEvent` names the event `41`, sent to a database whose latest event is `23`, EventSourcingDB answers with this error, as a line of the stream, and then ends the stream with its `end` item:

```json
{
  "type": "error",
  "data": {
    "code": "https://docs.eventsourcingdb.io/errors/last-backed-up-event-unknown",
    "description": "last backed up event is unknown: the store holds no event with its ID",
    "details": {
      "value": "41"
    }
  }
}
```