Standard or Enterprise Edition?

SQL-NS is available in four editions of SQL Server 2005: Developer Edition, Evaluation Edition, Standard Edition, and Enterprise Edition. The functionality of Developer Edition and Evaluation Edition is the same as Enterprise Edition; the difference is that Developer Edition is licensed only for development use and Evaluation Edition is licensed only for evaluation purposesneither can be put into production. Therefore, when comparing the editions, we usually distinguish only the Standard and Enterprise Editions in terms of SQL-NS features. Developer and Evaluation Editions can be substituted for Enterprise Edition in development and evaluation environments.

Caution

SQL-NS is not supported on the Express or Workgroup editions of SQL Server 2005.

Although the core SQL-NS functionality in the two editions is similar, the Enterprise Edition supports several features that make it more scalable and therefore capable of supporting the largest applications. Specifically, Enterprise Edition supports the following features, which Standard Edition does not:

• Distributed deployment With Enterprise Edition you can run different parts of your SQL-NS applications on different physical computers, enabling you to scale out your system.

• Thread pool and notification batch size settings Enterprise Edition offers options that let you fine-tune resource allocation so that you can precisely control how the workload of your SQL-NS application is handled.

• Multicast delivery For applications built on Enterprise Edition, you can choose to distribute the same physical notification to multiple subscribers, resulting in better performance. In Standard Edition, you have to distribute a separate notification for each subscriber.

It should be noted that even in the Standard Edition, SQL-NS does support very large applications because of the inherent scalability of the application model and execution engine. The Enterprise Edition features take scalability even further.

Because the SQL-NS components may be installed independently of the SQL Server used to host SQL-NS applications (especially in remote SQL Server configurations), it's possible for their respective editions to differ. For example, the SQL-NS tools and engine may be Enterprise Edition (because they were installed from a SQL Server 2005 Enterprise Edition CD), but the SQL Server itself may be Standard Edition. The following are the licensing restrictions on edition mismatches:

• Only Standard Edition or Enterprise Edition SQL Servers may be used to host databases for SQL-NS applications.

• The edition of the SQL-NS tools need not match the edition of the SQL Server against which they operate. For example, Enterprise Edition SQL-NS tools may be used to create a SQL-NS application on a Standard Edition SQL Server and vice versa.

• The edition of the SQL-NS engine used to run a SQL-NS application must be the same as the edition of the tools used to create the application.

The edition of the SQL-NS tools used to create an application determine the functionality that may be used in that application. For example, an application that uses multicast delivery, an Enterprise Edition feature, can only be built using the Enterprise Edition SQL-NS tools. Only an Enterprise Edition SQL-NS engine may run such an application.

You can use the SQL-NS tools and engine from either edition to work through the samples in this book. Subsequent chapters cover features that are available only in the Enterprise Edition (they are all marked as such), but those features are not used in the samples.