SQL Server knows two license models: Server/CAL and per core. In the past (version 2008/2008R2) SQL Server was also licensed per processor.
This licensing model is now only available for SQL Server Standard. It was also available for SQL Enterprise in the past, and you may have renewed Software Assurance for those licenses and still be using SQL Enterprise under that model. However, there is a limitation: a server license covers a maximum of 20 cores. If the SQL Server uses more cores, more server licenses are needed or you can switch to the per core licensing model.
A SQL Server requires a server license. For a user (or a device of that user), a CAL is needed. The user also needs a CAL if the user does not directly access the SQL Server, but uses an application that needs SQL. A CAL is also required for this indirect use. Under this model, a CAL is usually required for every user or device, because almost everyone uses some SQL-based application. A mix of user CALs and device CALs is also possible, but often difficult to manage.
It is also possible to pay SQL per core. This model is especially interesting if you would need many CALs or if the number of CALs is difficult to determine. No CALs are required under this model.
Physical SQL Servers require a license per physical core, with a minimum of four core licenses per processor (CPU, socket). Virtual SQL Servers require a license per virtual core, with a minimum of four licenses per VM.
If you assign SQL Enterprise core licenses to all physical cores in a server, a number of virtual SQL Standard and/or Enterprise servers equal to the number of core licenses assigned to the physical server may be used on that server. E.g. on a server with 20 physical cores, you may run up to 20 SQL VMs.
Benefits of Software Assurance
SQL server has a number of important advantages of Software Assurance (SA). In practice, licenses for SQL Server are usually purchased with SA.
Right to new versions
If Microsoft releases a new version during the term of the SA, that new version may be used.
Licenses for a virtual SQL Server are assigned to the physical server on which the virtual server runs. The license remains attached to the physical server for a minimum of 90 days. So if the virtual server moves to another host, the new host must also be licensed. In that case, two licenses are needed for one virtual server. In addition, if the VM moves across many hosts in a data center, many licenses are needed for that server.
Software Assurance adds the License Mobility right to a license, allowing the SQL VM to carry the license from host to host. This prevents the need for many licenses for one SQL VM.
In addition, License Mobility offers the right to use SQL servers on shared servers with third parties (service providers, outsourcers).
If all cores of a physical server are assigned SQL Enterprise licenses with SA, an unlimited number of SQL VMs can run on that server. That can make it very profitable to build a SQL Cluster. Without SA, the maximum number of SQL VMs is equal to the number of core licenses granted. With SA, the number of SQL VMs is unlimited.
Failover Privileges for SQL Server
For each of the Client's Primary Workloads, you are entitled to:
- one Failover OSE for any purpose, including high availability, on a Server solely for your use; and
- two Failover OSEs specific to disaster recovery:
- one on a Server dedicated for your use and
- one on Microsoft Azure servers.
Azure Hybrid Benefit
Licenses with SA may also be used in Azure, under the terms of the Azure Hybrid Benefit.
Power BI Report Server
SQL Server Enterprise licenses with SA may be used to run Power BI Report Server.