Note: ArcSDE software, including the application server, command tools, and SDK with C and Java APIs, was deprecated at ArcGIS 10.2.2 and is no longer distributed.
In some cases, upgrading to newer releases takes a phased approach where clients are upgraded first and the geodatabase is upgraded at a later date. Clients using ArcGIS 10.3 through 10.6 can connect to a 10.2.x application server. At ArcGIS 10.6.1, these types of connections do not work. ArcGIS Pro does not support connections to the ArcSDE application server.
Note: ArcGIS software features are deprecated, rather than immediately removed, to provide customers with backward compatibility and give as much advance notice as possible to adopt newer technology.
The ArcSDE application server was replaced by the ability to directly connect to an enterprise geodatabase from an ArcGIS client; this is referred to as 'direct connect'. Direct connect is the supported way to make connections from an ArcGIS client to an enterprise geodatabase or database. The Create Database Connection geoprocessing tool replaced the Create ArcSDE Connection File tool at ArcGIS 10.1.
The ArcGIS 10.2.x release reached its mature support phase in July 2017. No software patches or hotfixes are provided when software is in the mature phase. See the Esri Product Lifecycle Policy for more information. Additionally, no further development is performed on deprecated features.