For databases in a hierarchical configuration, every database has a single parent database, except the consolidated database, which has no parent.

SQL Remote supports hierarchical configurations of databases; it does not support peer-to-peer synchronization or other non-hierarchical configurations. MobiLink is also normally used with a hierarchical configuration, but can also be used in other configurations.

For any two databases directly sharing data in a hierarchical configuration, one is always above or below the other in the hierarchy.

Databases in a non-hierarchical configuration do not have a well-defined notion of above or below.

In a MobiLink or SQL Remote system, each database contains all or a subset of the data replicated by the database above it in the hierarchy.

Remote databases can contain tables that are not present at the consolidated database as long as they are not involved in synchronization. SQL Remote requires that the table and column names in the remote databases match the ones in the consolidated database. In contrast, MobiLink allows data to be stored in different columns and tables in the remote databases than in the consolidated database, allowing greater flexibility.