On rare occasions, you may find that a file geodatabase has been damaged and can no longer be opened. This usually occurs because one or more the files in the file geodatabase directory have been deleted. Frequently, these files include the system schema tables (which contain the file names) and the geodatabase metadata (GDB files) defining the relationships and complex data types (topologies, geometric networks, and so on). The Recover File Geodatabase tool works by opening each of the tables in the damaged file geodatabase directory, reading the file's header, and creating a copy of the table in a new file geodatabase. If the system schema tables are still present, then table names will be preserved; if not, names will be assigned.
The Recover File Geodatabase tool can only recover simple (point, multipoint, polyline, polygon) feature classes and tables. Complex data (annotation, raster datasets, networkdatasets, geometric networks, etc.) and relationships will not be recovered.