You have and Office 365 subscription and an on-premises deployment of Active Directory. You deploy Microsoft Azure AD Connect. Currently, the synchronization process is running. You need to modify the synchronization schedule. Which task should you perform first?

The sync engine processes identity information from different data repositories, such as Active Directory or a SQL Server database. The sync engine encapsulates interaction with a connected data source within a module called a Connector. Each type of connected data source has a specific Connector. The Connector translates a required operation into the format that the connected data source understands.
References: https://docs.microsoft.com/en-us/azure/active-directory/connect/active-directory-aadconnectsync-understanding-architecture