How to handle an unlicenced server?
Tableau offers two licensing models: user-based and core-based. User-based licensing requires each active user account to be covered by a license. User-based licenses have a defined capacity, or number of users that it allows. Each user is assigned a unique user name on the server and is required to identify himself when connecting to the server.
Core-based licensing has no constraints on the number of user accounts in the system, but it does restrict the maximum number of processor cores that Tableau Server can use. You can install Tableau Server on one or more machines to create a cluster, with the restriction that the total number of cores in all the machines does not exceed the number of cores you have licensed and that all of the cores on a particular machine are covered by the license.
Unlicensed User-Based Server
The most common reason for a server that has user-based licensing to be unlicensed is an expired product key or an expired maintenance contract. You can see your products keys and add new ones by selecting Start > All Programs > Tableau Server > Manage Product Keys.
Unlicensed Core-Based Server
A core-based server can become unlicensed for a variety of reasons. A common problem is that the primary or a worker node has more cores than the license allows. When the server is unlicensed you may not be able to start or administer the server. You can, however, manage your licenses using the tabadmin command line tool. Follow the steps below to see a list of your licenses and number of cores by machine.
Open a command prompt as administrator and navigate to the Tableau Server bin directory. For example, on a default install, type the following: cd C:\Program Files\Tableau\Tableau Server\10.3\bin
Type the following: tabadmin licenses -p.