I am sure there is no undo. Curious as to what is so bad that you would want to rollback? I would also note that you should be considering upgrading at some point since 11.1 is off support. 

The only way I would see to roll back would be to restore a snapshot or back up of the entire system. Each update or upgrade should be done with a restore point if something goes wrong.  The problem is that you mentioned it has been some time. This means that you've likely been in operation creating new data. I do not think those things are separable so unless you also roll back vaults, DB, LDAP to a common sync point, I think its too much effort. Sorry for not so good answer.