If a new version of the operating system is included in the new Delphix version, then your Delphix Engine will automatically quiesce all VDBs and dSources during the upgrade process in order to safely reboot to the new version.

At the end of the upgrade process, the Delphix Engine will also update the Delphix platform toolkit on each connected environment.

To perform these tasks, the Delphix Engine must be able to connect to the environments in which datasets exist and must have credentials to connect to datasets or applications. Environments involved must be properly configured to enable script execution.

When an environment, dataset, or application is unreachable or misconfigured, the upgrade may encounter access errors, and may not be able to re-start it after the upgrade has been applied.

If you know that a dataset is unavailable for some reason (e.g. host not reachable on the network, or the hosting server is down), it is recommended that you disable it (if necessary utilize Force Disable). 

The Impact of Upgrade section in the Details tab contains the list of datasets which have been identified as unreachable, misconfigured or not behaving correctly and are at risk of not functioning after the upgrade.

Review the warnings in this section (if any) and take appropriate actions before applying the upgrade.