Review these topics to understand and to use the Pre-Upgrade information tool (preupgrade.jar).

• Setting Up Environment Variables for the Pre-Upgrade Information Tool
  Before you run the Pre-Upgrade Information Tool, in preparation for your non-CDB upgrade, set up the user environment variables for the Oracle user that runs the tool.
• Running the Pre-Upgrade Information Tool
  To check your system and database to see if it is ready for upgrade, use the Pre-Upgrade Information Tool (preupgrade.jar)
• Pre-Upgrade Information Tool Warnings and Recommendations for Oracle Database
  Analyze any Pre-Upgrade Information Tool warnings before you upgrade to the new release of Oracle Database. For each item that the tool reports, it provides you with information about how to fix the issue or warning.
• Pre-Upgrade Information Tool Output Example
  In this example, you can see how the Pre-Upgrade Information Tool displays recommended fixes, but does not carry out fixes automatically.