Database - Best Practice For Upgrading To Latest Patchset With CPU/PSU And One-off Patches

To minimize downtime that is caused by patching and upgrading Oracle RDBMS, consider the following upgrade methodology;

--First update the software, then update the database--

Here are the steps based on the above methodology:

• Install the patchset (suppose 11.2.0.3)
• Apply the latest PSU or CPU
• Apply any mandatory/recommended/required patches for the environment (gather this information from -> known issues and alerts of  10.2.0.4 for example, or related application documentation, interoperability notes)
• Upgrade the database --> Actual upgrade (for example catupgrd.sql) and execute post installation instructions
• execute PSU or CPU post installation instructions. 
• execute post installation instructions of mandatory/recommended/required patches that are applied above (if any)

Note that: The post installation instructions of PSU/CPU and any other patches applied after the upgrade, should be executed not only on upgraded databases, these instructions should be executed on newly created databases which are created by using dbca sample templates (general,transaction processing, data warehouse).  Because these templates are based on the pre-created data files.(not patchted , not psu applied)

If database is created using custom option or sql "Create database.." , no need to execute the post install instructions of PSU/CPU or any other patches, as these creation methods actually create the database using existing/updated/patched binaries in Oracle Home .