Installing IBM i 7.4 over IBM i 7.2
If you are installing IBM® i 7.4 over IBM i 7.2, you should also read the IBM i Memo to Users for IBM i 7.3. It contains incompatibility-related information about the new functions and enhancements incorporated in IBM i 7.3.
You can also view the IBM i 7.3 IBM i Memo to Users in the IBM Knowledge Center under the IBM i 7.3 release :