Excellent question. We're glad you asked!
Because the Delphix Engine provides storage to your target environments, for VDBs and staging databases, it is important not to shut it down without gracefully shutting down the databases that depend on it. Failure to do so will result in NFS or iSCSI I/O errors on the target environments.
Prior to shutting down the Delphix Engine, all VDBs should be shut down through the Delphix UI (via GUI, CLI, or Web Services APIs). In addition, all staging databases should be disabled. This includes all SQL Server dSources, and any Oracle dSources for which pre-provisioning is enabled.
To shut down the Delphix Engine, log in to the Server Setup UI as sysadmin and click the "Shutdown Delphix Engine" link, then the "Power Off" button. Or, log onto the CLI as sysadmin@SYSTEM, and enter "/system/shutdown" followed by "commit". If no one is available to log on as sysadmin, it is also acceptable to use the "Shutdown Guest" function from within VMWare, which will cause an orderly shutdown of the Delphix Engine. Avoid using the "Power Off Guest" function without first shutting down the Delphix Engine, however!