The Online customer database uses SQL Server change tracking to manage all tables that are subject to mirroring.
SQL Server change tracking is a light-weight mechanism implemented directly in the SQL Server database engine. It uses an incremental 64-bit integer, Log Sequence Number.
Using this method, rather than the internal
TravelTransactionLog, avoids complexity in the following situations:
- UDEF changes
- Merging 2 companies is logged differently from other operations
- Service operations are not logged at all in
How does it work?
- When change tracking for a table is OFF, it is automatically turned ON by the mirroring system.
- A wipe message is sent to the client.
- All records in the table are considered changed and therefore transmitted to the client.
How long is tracking data kept?
Change tracking data is kept for 7 days.
If a mirroring client service is down for more than a week, change data will be missing and the next synctronization will therefore cause a complete, automatic repopulation of the mirror.