How have enterprise geodatabases evolved since ArcGIS 10.0?

Answer

The following is a list of changes made to the enterprise geodatabase user experience since ArcGIS version 10.0.

Starting at version 10.0, Esri began to move some of the functionality we historically saw in the SDE post-install and SDE command line tools into the main ArcGIS for Desktop application.

At 10.0:

• We added the ability to upgrade the geodatabase using ArcCatalog within the database properties window.
• Behind the scenes, the geodatabase repository tables are condensed. This is done partly by using XML columns in GDB_ITEMS to store information related to the data in the geodatabase (the database must be able to use these xml columns).

At 10.1:

• It is no longer necessary to install the Post Installation wizard. The wizard defined the database and sde user, created the sde repository, authorized the user sde with the .ecp license, and created the application server service.  At 10.1, we packed the first three operations into the Create Enterprise Geodatabase tool and the Enable Enterprise Geodatabase tool, as discussed below.
• If choosing to continue using Application Server Connections from version 10.1 and newer, ArcSDE software associated with your RDBMS platform and Arc versions must be installed (for example, your ArcSDE 10.2.2 software).  Since the first three tasks of the post-install were moved into geoprocessing tools, and we are suggesting moving away from application server connection and move towards direct connect, it is slightly more complicated to make server connections, for example, it requires an extra installation of the application server connection software and some extra administrative maintenance. 
• If choosing to continue using application server connections, it is also necessary to use command line tools for some of the commmands specific to monitoring the service. Most other commands will be redundant since they are packaged into the geoprocessing tools. These can be scripted to Python and ran as tasks if necessary:  See the following article: Do This, Not That! – Alternatives to using SDE command line tools
• If choosing to continue using application server connections, it is necessary to create the application server connection from ArcCatalog using the Create ArcSDE Connection File. This is another example of how the newer versions encourage direct connects by making the use of application server connections not as convenient. See the following article: How To: Make an application server service connection (3-tier) to ArcSDE using ArcGIS 10.1
• The Database Connections dialog box has been simplified to require less input to make a connection, and functionality has been expanded to allow connections to any supported database, even if it does not contain an enterprise geodatabase.  Previously, it was required to use OLE DB connections when working with databases from ArcGIS for Desktop.  See the following article: Database connections in ArcGIS for Desktop

At 10.3:

• We no longer offer the ArcSDE application server connection software. Connect to all databases in ArcGIS for Desktop 10.3 using direct connections.  You can also use existing SDE files created from application server connections and create application server connections to services from previous versions. See the following article: Where is the install for ArcSDE 10.3?

At 10.4:

• Connections using application server connections are deprecated.  It is no longer possible to connect to any geodatabase using application server connections from this client version. Everything must use direct connect. It is important that existing map documents and connection files be updated from application server connections to direct connections before the client upgrade to 10.4.1