Please be aware that if you have an Oracle database and the Oracle Critical Patch Update (CPU) released on October 14th, 2014 has been installed, ArcGIS is no longer able to connect to the Oracle database and the application will hang or crash. This affects all versions of ArcGIS Desktop, and will also impact ArcGIS Server and other products.
. If you have not yet installed this Oracle patch, you are advised to not install it until the issue has been resolved.
. If you have installed the Oracle patch, you are advised to roll it back to restore normal operations.
Esri and Oracle are working closely to understand and resolve the problem.
For more information and any new updates on the issue please see Esri Knowledge Base article 43293
Patches are now being released for this issue; see this article showing the list of available patches for your specific ArcGIS version.