Oracle has many variants of patches, which are available in the Oracle database, Enterprise Manager, Fusion Middleware, WebLogic, Java and the other products.
Critical Patch Update (CPU) now refers to the general release of quarterly security fixes, rather than the cumulative database security update for the quarter. Think of the CPU as an overall quarterly release, rather than as a single update.
Patch Set Updates (PSU) are the same cumulative updates which include both security fixes and priority fixes. The key with PSUs is that they are minor version upgrades (e.g. 11.2.0.1.1 to 11.2.0.1.2). After a PSU has been used, it can only be used in future quarters until the database has been upgraded to a new database version.
Security Patch Update (SPU) terminology was introduced in the Critical Patch Update in October 2012 as the term for the quarterly security update. SPU patches are the same as previous CPU patches, just with a new name. For the database, SPUs cannot be used once PSUs have been used, until the database has been upgraded to a new base version.
Bundle Patches are the quarterly patches for Windows and Exadata, which include both the quarterly security updates and recommended fixes. Interim Patches are also available for fixing specific bugs, along with Diagnostic Patches which are solely applied for the purpose of retrieving more information in order to fix a problem. More details can be found in MyOracle Support document ID 1430923.1.
Through its Managed Services solution, Cegal can issue recommendations and perform the patching itself based on recommendations from Oracle. Cegal already does this for many customers, which means it can do it both efficiently and securely.