A point of contention and confusion regarding Oracle Critical Patch Update (CPU) database patches is that only a limited set of database patchsets are supported. For the January 2008 CPU, only the patchsets 126.96.36.199, 10.1.0.5, 10.2.0.2, 10.2.0.3, and 188.8.131.52 are supported. Oracle's policy is stated in the CPU Frequently Asked Questions (FAQ) (Metalink Note ID 360470.1) -
"As a general rule, Critical Patch Updates (CPUs) are created for the last two patch sets of Server Technologies releases during the period when a release is in Premier Support (under the Lifetime Support Policy) or Error Correction Support (ECS). However, in the case where the latest patch set of a release has been available for more than 1 year, CPUs will be provided only for the most recent patch set for that release. Once a release enters its Extended Support (under the Lifetime Support Policy) or Extended Maintenance Support (EMS) period, CPUs are created only for the last patch set of that release."
The "Database, FMW, and OCS Software Error Correction Support Policy Version 2.1" (Metalink Note ID 209768.1) provides more details on the CPU support policy, since there are a number of exceptions or deviations in the policy based on platforms and extended support. Appendix A gives exact timing for patchset support for the database and Fusion middleware, which is 1 year from the release of the most current patchset. For database versions under Extended Support, CPU patches will be available for the terminal patchset until Extended Support period ends.
Based on Oracle's policy, all organizations as a matter of policy should apply a database patchset at least annually in order to apply CPU patches on a timely basis. Oracle maintains strict adherence to this policy with few exceptions. With the release of 10.2.0.4 in February/March 2008 for Linux and other platforms, CPU support for 10.2.0.3 should be ending March 2009 -- this means no April 2009 CPU for 10.2.0.3. This support timeline can be problematic for some databases as the application may not allow or certify the newest patchset for a number of months, thus cutting this year to a few months in some cases.
(This may be difficult for many organizations to fathom since many have not yet applied April 2007 nor upgraded from 10.2.0.2.)