A vCenter Server upgrade can fail when the installer is unable to stop the Tomcat service.
Problem
If the vCenter Server installer cannot stop the Tomcat service during an upgrade, the upgrade fails with an error message similar to Unable to delete VC Tomcat service. This problem can occur even if you stop the Tomcat service manually before the upgrade, if some files that are used by the Tomcat process are locked.
Solution
Solution
Alternatively, you can restart the vCenter Server machine and restart the upgrade process, but select the option not to overwrite the vCenter Server data.