The Network Admin Updates Screen controls update process in the network. If an update is available, you᾿ll see a notification appear in the Toolbar and navigation menu. Keeping your site updated is important for security. It also makes the internet a safer place for you and your readers. There are two screens under the Network Admin > Updates. In the default Available Updates Screen , you can update WordPress, themes and plugins. After you updates to the latest version of WordPress, you can upgrade all the sites on your network from Upgrade Network Screen.
This Upgrade Network Screen is used to upgrade all the sites in a Network after a WordPress upgrade is completed. After a WordPress upgrade, you are reminded to visit the Upgrade Networks with a message such as, "Thank you for Updating! Please visit the Upgrade Network page to upgrade all of your sites."
The Upgrade Networks feature will step through each site, five at a time, and make sure any database changes are applied. This menu item is only visible if you are logged in as a Super Admin role user. You can access it from any site in the network.
If for any reason a site does not get upgraded, each site should be upgraded when the admin for that site logs in to the administration for that site. Sites that have been deactivated will not be upgraded by this process, however, if a site is reactivated, the site will get upgraded when an admin for that site logs in to the dashboard for that site.
If a version update to core has not happened, clicking this button won’t affect anything.