Hi,
I was helping a customer who wanted to be ready to migrate the database to 23c when it becomes available using zero or near-zero downtime upgrade techniques. Besides Oracle Golden Gate, one good technique to consider is using a logical standby database to perform a rolling upgrade of the Oracle Database.
Oracle Transient Logical Standby is a powerful feature within the Oracle Database ecosystem that enhances the availability and flexibility of your database environment and your production database incurs very little downtime during the upgrade process. The overall downtime can be as little as the time it takes to perform a switchover.
During a rolling upgrade, you can run different releases of Oracle Database on the primary and logical standby databases while you upgrade them, one at a time, incurring minimal downtime on the primary database.
If you are on Oracle Database 12c and have the Active Dataguard License, you should look at DBMS_ROLLING to Perform a Rolling Upgrade.
Links to help you understand how to use this approach:
Here you can find a webinar from our team covering this technique:
A good documentation:
https://www.oracle.com/technetwork/database/availability/database-rolling-upgrade-3206539.pdf
A presentation from the MAA team: https://oraclemaa.com/storage/2022/10/ADG_ROLLING_UPGRADE_LVOUG_v2.1.pdf
Demo: