ISSU and NSSU

Check is this ISSU feature is supported:   https://apps.juniper.net/feature-explorer/issu.html

ISSU: In-Service Software Upgrade

Upgrade routers with dual Routing Engines:
https://www.juniper.net/documentation/en_US/junos/topics/task/installation/junos-software-installing-on-dual-routing-engines.html

These are for ISSU:
-Verify unified ISSU support for your device
-Perform a unified ISSU
-Verify that the unified ISSU is successful
-Understand how the unified ISSU process works

https://www.juniper.net/documentation/en_US/junos/topics/concept/issu-oveview.html

Step-by-step example for ISSU:
https://www.juniper.net/documentation/en_US/junos/topics/task/installation/issu-upgrading.html

ISSU for QFX5100 ( not in virtual chassis )

https://nextheader.net/2015/09/24/in-service-software-upgradeissu-on-qfx5100/

NSSU:   Non-Stop Software Upgrade

https://apps.juniper.net/feature-explorer/feature-info.html?fKey=1175&fn=Nonstop%20software%20upgrade%20(NSSU)

>>>> /wiki/spaces/JS2/pages/350453869

Understanding the Unified ISSU Process

https://www.juniper.net/documentation/en_US/junos/topics/concept/understanding-issu-process.html

PTX Software Features:

https://apps.juniper.net/feature-explorer/select-platform.html?category=Routing&typ=1#family=&pid=51601000&platform=PTX1000&rel=18.3R1&sid=916&stat=0.18525285899184607&swName=Junos+OS