In Sitecore 9+, xDB data can be stored in SQL databases. To ensure the performance, Sitecore uses Shard databases, see Jason article Sitecore 9 xDB Sharding . The sharding data is managed in ShardMapManager table, which stores the server name and database. It works like a charm, but just one issue. The server name and database is hard references, which can cause problems for data migration. If you are trying to create a Sitecore instance from database dumps, the DatabaseName and ServerName need to be updated in [Xdb.Collection.ShardMapManager].[__ShardManagement].[ShardsGlobal]