how to restrict users to access tempo site?

Yes - just remove everyone from the group "Tempo Users".

Thanks Mike, but it has a predefined membership rule to add all users into this group. I can delete this rule but it requires appropriate approval. appreciate if you can share any alternative solution.

Thanks/Mp

Yes, removing or revising the Tempo Users group membership rule is the one and only way to accomplish this.  If you don't have access to changing the rule, you should discuss this with whoever administers your Appian installation.

Thanks Mike! I am an APPIAN admin, but the challenge for me is, all the end users of an application which I recently taken over are accessing their tasks, reports & action through tempo site though we have application specific sites. I agree this is not an APPIAN best practice. How do I overcome this challenge? Is it through educating the end users about Appian best practices?

Why don't you just add a page to the new site which has the tasks actions and reports? I think it's a pretty common pattern to have a dashboard approach where the first page in a site has these types of objects anyways.

Set up a "tasks" interface in all the user-accessible Sites where a user can see their own tasks (following any of a number of standard "tasks by task report" recipes, i have a full working implementation of that on the App Market in the form of my "Advanced User Task Report" app if that helps).

After that, make sure all end users are in a group which has a designated site for a User Start Page.  Basically ensure that users logging in never land on "/tempo" by default, but instead see their targeted site.  After you're sure that users no longer rely on Tempo, then you can restrict access to it for basic users.

Set up a "tasks" interface in all the user-accessible Sites where a user can see their own tasks (following any of a number of standard "tasks by task report" recipes, i have a full working implementation of that on the App Market in the form of my "Advanced User Task Report" app if that helps).

After that, make sure all end users are in a group which has a designated site for a User Start Page.  Basically ensure that users logging in never land on "/tempo" by default, but instead see their targeted site.  After you're sure that users no longer rely on Tempo, then you can restrict access to it for basic users.