The following approach is generally recommended for monitoring the health of your vCenter servers:
Install an agent on the vCenter server to monitor its overall performance and system health. Use the Windows Service Check monitor to verify that the following services are running:
VMware Infrastructure Web Access;
VMware License Server (if it is running on the target vC install); VMware VirtualCenter Server.
Use the HTTP monitor to ensure that the /ui/ page is responding to web requests on the vCenter Server.
Monitor the following on the vCenter MSSQL/Oracle DB server:
tablespace capacity;
connectivity using the basic monitor for the appropriate DB type;
system application event logs for error level events.
Monitor the file system capacity of the volumes hosting the vCenter application and database files.
Monitor the application event log of the vCenter server, specifically searching for Error events within the VMware VirtualCenter Server source.