First, here is the main Vantage maintenance link to use:
Second, to perform a Web Client upgrading the same rule applies each time.
1) Backup your ZFS files for Install, Runtime and Webclientdb
2) Stop VANWEBUI
3) Create or empty the install and runtime directories.
Notice that once you will have upgraded the database you will not be able to return back.
4) Download the new pax file and copy it into the empty install directory.
5) Unpax it and run the install processing
6) At time you will be asked for the Vantagedb, do not create it but reuse it by specifying its actual path location.
7) Once the installation is successful then connect with APP user after restarting the VANWEBUI STC. The connection will proceed with the upgrading and stops.
8) Reconnect using APP userid again to create and upgrade the Vantagedb. Reply yes to any messages appearing
9) Once done, disconnect from APP and connect using your normal TSO userid.
So for the upgrading, you need to only stop the Web Client STC. No IPL or any impacts on the MVS side except if you define new path for the upgrading, you will need to update the SYS1.PARMLIB(BPXPRMxx) member to mount them at IPL.