Short anwser: The newest one you can get on the day you are reading this.
The long answer: All the features i’m writing about in the last few days didn’t appeared with a single SRU in Oraacle Solaris 11.4. They were introduced to Solaris over a longer period with time. That said i decided not to mention which SRU brought the feature into Solaris. If it not works in your currently installed version or if it’s not mentioned in the man page, just assume it’s the latest, most current version of Solaris 11 that will get you the feature. Because this is the SRU you want.
At the end you would update it to this version and not to the minimal version to get the feature. There is no point in updating for example to SRU25 today, because a feature appeared there when there is already a SRU 30 available. You would run a 5 months old operating system and nowadays it’s more essential to be as current as possible with your systems than ever.
Features like IPS, boot environments and so on makes it much easier to stay on top of this. So patch early and patch often. At least the quarterly CPU.
