> ## Documentation Index
> Fetch the complete documentation index at: https://docs.superoffice.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Database Mirroring scenarios

> How the Database Mirroring client handles common situations - new customers, backups, restores, downtime, schema changes.

The system is largely self-bootstrapping. The table below summarizes what happens in common situations.

## Scenarios that are handled

| Action                                        | SuperOffice cloud                                                       | Customer / client                                                                                                                                                                                     |
| --------------------------------------------- | ----------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| New customer                                  | CDC is enabled at the source. An initial snapshot is published.         | The client provisions, performs the initial snapshot, and starts long-polling for changes.                                                                                                            |
| Replica restored from backup                  | Ordinary streaming continues.                                           | Kafka offsets travel with the replica (stored in `_ReplicationState`). The client resumes from where the restored snapshot left off. Any changes published after the offset are received and applied. |
| Source database restored from backup or moved | Tenant-operations sagas reset the offsets and trigger a fresh snapshot. | The client receives upserts for the snapshotted rows and reaches a consistent state automatically. No manual intervention.                                                                            |
| Writing to the replica fails                  | Streaming continues.                                                    | The client retries the failed batch. Progress is only committed when a transaction succeeds. Subsequent retries pick up where the last successful commit left off.                                    |
| Client is offline for **less than 7 days**    | Events accumulate in Kafka.                                             | The client resumes from the saved offset and replays the buffered events.                                                                                                                             |
| Client is offline for **more than 7 days**    | Events have been purged from Kafka.                                     | The client cannot fill the gap by replay. Run [`resync-tables`][2] on the affected tables (or, in extreme cases, request a full reset from SuperOffice Operations).                                   |
| New table added in SuperOffice Service        | The schema is detected by the connector and published.                  | On the next schema-check cycle (default: hourly, `SchemaUpdateIntervalSeconds`) the client picks it up and snapshots it. Force immediately with `update-schema`.                                      |
| Incompatible schema change (rare)             | A schema event is published.                                            | The client drops the affected table in the replica, re-creates it with the new schema, and requests a fresh snapshot for just that table.                                                             |
| Tenant suspended / resumed                    | Provisioning sagas pause and then reset offsets.                        | The client absorbs the resulting snapshot as upserts and continues.                                                                                                                                   |

## Related

* [Set up the Database Mirroring client][1]
* [Force re-sync][2]
* [Change tracking][3]
* [Troubleshooting][4]

[1]: ./setup-guide

[2]: ./force-resync

[3]: ./change-tracking

[4]: ./troubleshooting


## Related topics

- [Database mirroring](/en/online/mirroring/overview.md)
- [Order database mirroring](/en/online/mirroring/order-database-mirroring.md)
- [Database Mirroring requirements](/en/online/mirroring/requirements.md)
- [Troubleshooting Database Mirroring](/en/online/mirroring/troubleshooting.md)
- [CRM Online Database Mirroring](/en/api/nuget/crm-online-mirroring.md)
- [Set up the Database Mirroring client](/en/online/mirroring/setup-guide.md)