DATABASE MIRRORING AND SQL SERVER 2012 EDITIONS

Now that you understand the operating modes of database mirroring, it is a good idea to keep in mind which of these operating modes is available on your edition of SQL Server. Table 19-2 summarizes which features of database mirroring are available in which SQL Server 2012 editions.

TABLE 19-2: SQL Server 2012 Features Supported by Edition

The SQL Express edition can be used only as a witness server in a mirroring session. Some other features such as high-performance operating mode, you need the Enterprise or Developer edition.

SQL Server 2012 may use multiple threads to roll forward the log in the redo queue on the mirror database. This is called parallel redo. If the mirror server has fewer than five CPUs, SQL Server uses only a single thread for redo. Parallel redo is optimized by using one thread per four CPUs. This feature is available only in the Enterprise or Developer editions.