What are the series of tables in a database whose names start with 'GDB_'?
Last Published: April 25, 2020
Those series of system tables are used by each geodatabase to manage relationship classes and rules. In an ArcSDE geodatabase, the SDE user may own these tables.
These system tables are managed automatically by the geodatabase. Never manually manipulate these tables. Doing so may cause corruption of the geodatabase and would require restoring the data from backup.
The structure of the geodatabase is detailed in the following ArcGIS Desktop help topics: