Concur with Phil.
“Fail to prepare, prepare to fail”.
For 7.8…x to 7.9.x you’re looking at a minimum of one 15 minute outage. Prior to the day planned as per attached PDF, I took a GWBK and ran in a sandbox with 10X testing for a month (10X means, if normally 3K tags, use a script to generate another 27K, if normally 10 clients open, run 100, etc). Contact your IA sales rep and they should assist with a 30-day temp licence for this, or if you are an Integrator, avail of your R&D license.
A 7.9.1 to 7.9.18 should be basically the same, in theory should run smoother.
A 7.9.18 to 8.1.12 will have a lot more steps and more downtime, requires more testing in the sandbox.
SCADA Upgrade (Redacted) V2.0.1.pdf (73.0 KB)