TO understand this concept, please first understand the difference between a service and the database. WIndows NT service MUST exist in order to start or create a new database. For exmple suppose your database sid is TEST, then OracleServiceTEST MUST have been started before you create or start this database. This service communicates with Windows NT OS on behalf of your database.

In simple words service is a coordinator between database and OS.

SVRMGRL is not used to stop/start the database.
Database is started/stopped through services only.

Prince please understand basics before you start giving your opinions on this forum.