You must be at least on Oracle Database 19c to upgrade to the next Long Term Support release. You cannot upgrade from 11.2.0.4 or 12.1.0.2 to Oracle Database 23c directly. You must upgrade to Oracle Database 19c to upgrade to Oracle Database 23c.
The next Long Term Support (LTS) release of Oracle Database (Oracle Database 23c) is available for upgrade from either Oracle Database 19c or Oracle Database 21c. The next Long Term Support (LTS) release of Oracle Database is not available for upgrade from:
- Oracle Database 18c
- Oracle Database 12.2.0.1
- Oracle Database 12.10.2
- Oracle Database 11.2.0.4, or any older versions.