WebLogic Major Upgrade Without Downtime
A trip down memory lane… A long time ago, in 2015, we were running an Oracle WebLogic 11G cluster, which needed to be upgraded to 12C. However, Oracle did only support rolling upgrades for minor versions, not for major versions… In the image above, you see a simplified layout of our cluster (there were more servers and instances in the real setup). Traffic comes in from the left, via a load-balancer (and some apache’s). It was spread across the managed…