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 (vmdir) is the underlying LDAP service that vCenter SSO depends on. If vmdir cannot be stopped during the upgrade process, the SSO component installation will fail. Manually restarting it confirms it can stop and start properly, clearing the blocker for the upgrade.

Restarting the SSO service itself does not resolve the underlying issue because the failure is caused by the VMware Directory Service dependency, not the SSO service process itself.

Uninstalling SSO would destroy existing identity and authentication data and is not a supported step in the upgrade path.

Uninstalling the VMware Directory Service would permanently remove the identity store, breaking authentication for the entire vSphere environment.