Answer: Use the .tar.gz files of the concerned platforms to upgrade the SD-WAN software to 9.3.x. After the SD-WAN software is upgraded to 9.3.x version, perform change management using the .zip package to transfer/stage OS component software packages. After activation, the MCN transfers/stages OS components for all the relevant branches.

Question: After upgrading to 9.3.0 using single step upgrade package (.zip file) do I need to perform .upg upgrade on each appliances?
Answer: No, OS software update/upgrade will be taken care by the single step upgrade .zip package and it is installed as per the scheduling details provided by you in the Change Management Settings of the respective sites.

Question: Why should I use .tar.gz followed by .zip package to upgrade from pre-9.3 to 9.3.x , and why not directly use .zip package of 9.3.x?
Answer: Single Step upgrade package is supported from release 9.3.0 build 161 onwards. On earlier release versions (prior to 9.3) this package is not recognized. When the single step upgrade .zip package is uploaded into the Change Management inbox, the system throws an error stating that the package is not recognized. Hence, first upgrade the SD-WAN software to release 9.3 or above version and then perform Change Management using the .zip package.

Question: How will the OS Components be installed through single step upgrade, if .upg upgrade is not performed?
Answer: The MCN will transfer/stage OS components software packages based on the appliance model, after the Change Management is completed using single step upgrade .zip package. After activation, the MCN starts transferring/staging the OS components software packages for the branches that need them for the scheduled update/upgrade.

Question: How do I install OS components, without scheduling for later installations?
Answer: Set the Maintenance Window value to ‘0’ for instant installation of the OS components. 
               Note: The installation will start only when the appliance has received all the package that are needed for the site, even when Maintenance Window value is set to ‘0’. 

For latest update and additional FAQ's refer https://docs.citrix.com/en-us/netscaler-sd-wan/9-3/faqs.html