Geodatabases are the central store for maintaining all your vector data for ArcGIS. Traditionally data integrity in a geodatabase is maintained with the use of versioning. Edits are made in a version. The data is quality checked and then published to the control version.
We are seeing an increasing need to maintain more than one copy of data with the advent of ArcGIS Online. Data is moved to cloud servers and ArcGIS Online to allow field editors and remote offices access to the corporate datastore. The concept of one centralised database is being eroded because of these requirements for multiple sources. Enter the geodata service. Residing on top of a versioned geodatabase, the geodata service allows organisations to replicate data through the firewall to cloud servers and ArcGIS Online – allowing users in remote office and field users to have access to and update the most current data.
Another common scenario is to have the GIS data in one geodatabase and corporate data in another. The ability to directly connect to these enterprise databases in ArcGIS and join and manipulate data is also highlighted.
Gordon S
Esri Australia Technical Blog 