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 or 21c 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.
Look at this newly updated timeline (Updated on February 2024) for Oracle Premier and Extended Support:
As you can see, Oracle extended their 19c support to April 30, 2026. They also provided Oracle Database 21c customers another year of support.
Oracle Database 23c release date is expected to be sometime middle of this year.