When upgrading vCenter Server, an administrator notices that the upgrade fails at the vCenter Single Sign-On installation. What must be done to allow the upgrade to complete?

The VMware Directory service is a core dependency of vCenter Single Sign-On. If it cannot be stopped gracefully, the SSO upgrade step will stall or fail. Manually restarting the VMware Directory service confirms it can cycle through stop and start states, clearing the blockage and allowing the upgrade to proceed.

Restarting the SSO service itself does not address the root cause - the underlying VMware Directory service is the dependency that must be verified, not the SSO service layer above it.

Uninstalling SSO is a destructive action that is not required and would break the existing authentication infrastructure rather than resolve the upgrade failure.

Uninstalling the VMware Directory service would destroy the identity store and is not a valid troubleshooting step for an upgrade failure.