Enterprise Manager 220.127.116.11 has now been released for a few weeks, as well as the 18.104.22.168 OMS Bundle patches (also known as System patches). If you plan to apply these bundle patches to your 22.214.171.124 OMS, and you are concerned about the downtime, then, you can reduce the downtime by referring to this whitepaper that contains patching instructions to reduce downtime.
This whitepaper covers various Enterprise Manager High Availability (EM HA) usecases (level 1, 2, 3, 4), and contains instructions on how to reduce downtime while applying patches to each of these usecases. It also clearly defines the steps that require downtime and those that do not.
If you have a multi-OMS setup, you can also refer to this whitepaper which covers script creation using the opatchauto command, which automates the substeps and further reduces downtime.During our internal testing of this whitepaper on an EM HA setup, we have noticed a significant reduction in downtime.
If your customer plans to do an Enterprise Manager Upgrade to 126.96.36.199, then as a post upgrade recommendation, they should patch their OMS with the latest bundle patches by following the instructions outlined in this whitepaper
White paper on OTN:
MOS note for the latest Bundle Patches:
Enterprise Manager 188.8.131.52.0 (PS3) Master Bundle Patch List (Doc ID 1900943.1)