Next I upgraded Portal to 18.104.22.168.
Next I installed current CF for portal (CF14)
All was working as expected.
Next I installed CF49 for WCM. It did not install correctly so I had to uninstall.
After uninstalling, I could not connect correctly to DB2.
The problem returned was that in the title of this post.
In order to diagnose this, I initially attempted to use Portal ConfigEngine validate-database-connection. This gave no joy. Next I tried the db2 command prompt.
Sure enough the issue was at DB2 level since I could no longer login to any database.
Searching around gave the the answer:
My DB2 installation is a "non-root" install. Apparently Server authentication is not enabled during a non-root install.
So to fix this I simply needed to enable server authentication with:
$ su root
This seemed to do the trick and now Portal can connect to DB2 without issue.
Note that this only seemed to be in an issue after upgrading to 22.214.171.124 , with a failed installation of a CF. Before that failure of the CF, all was well
Hope this saves someone some time.