Database Specific Aspects of 64-bit Development
Since at design-time Rad Studio XE 2 works only with x32 libraries and if a connection to the server is needed at design-time, you need to install Oracle Client (x32) regardless of the intended platform. (If the x32 client is needed only for development, you can use only Oracle Instant Client). By default, ODAC use DEFAULT of Oracle Client, that is why, if a x64 client is the default client at design-time, you need to specify a x32 client. To prevent conflicts between different versions of Oracle Client on the end-user side, you can leave the Home property empty, in this case, the default client will be used.
Since there is no need to install Oracle Client for the DIRECT mode, the development of applications for the x64 platform does not differ from the development of application for Windows x86.