CertSrv.exe is the Server Engine program that is executed when the Certificate Authority service runs. In ordinary use, CertSrv should be started as a service automatically or manually through use of the Services applet in the Control Panel. It can also be started manually as a service using the following syntax:
net start "Certificate Authority"
Or use the short name for the Certificate Authority service as shown here:
net start CertSvc
For troubleshooting purposes only it may be desirable to run CertSrv as a stand-alone application in a Command Prompt window. When CertSrv is running in the diagnostics mode it displays a log of its actions in the console window.
where the command line option is as follows:
-z Runs CertSrv as a stand-alone application in a diagnostics mode for troubleshooting purposes only. If CertSrv is started from the command line without the -z option, there will be a delay and then the server will run in the diagnostics mode.