Behavior Changes to SQL Server Features in SQL Server 2012
This topic describes behavior changes you might see when you upgrade to SQL Server 2012 from a previous version of SQL Server. Behavior changes affect how features work or interact in SQL Server 2012 compared to earlier versions of SQL Server.
If you are upgrading from SQL Server 2005, we recommend that you also review the content in the SQL Server 2008, and SQL Server 2008 R2 sections.
If you are upgrading from SQL Server 2008, we recommend that you also review the content in the SQL Server 2008 R2 section.
SQL Server Multi-Subnet Failover Cluster
For multi-subnet failover cluster installations, upgrade from SQL Server Developer or SQL Server Evaluation to SQL Server Standard is not supported.
SQL Server multi-subnet failover clusters are supported on Windows Server 2008 R2 or later versions.
For more information, see SQL Server Multi-Subnet Clustering.
SQL Server Failure detection in SQL Server Failover Cluster
In SQL Server 2008 R2 and earlier versions, SQL Server reported failures to the Windows Failover Cluster service by running the "SELECT @@SERVERNAME" query. If the query did not run successfully, it resulted in a failover or restart of the SQL Server resource.
Starting in SQL Server 2012, failure detection process no longer uses the "SELECT @@SERVERNAME" query, but includes the following capabilities:
Monitoring major SQL Server components
Setting conditions for SQL Server failover or restart
For more information, see Failover Policy for Failover Cluster Instances.
The default failure condition level in an instance of SQL Server 2012 failover clusters is closest to the failure detection behavior of the previous versions of SQL Server. However, at this failure condition level, SQL Server may not detect query processing failures which may have been detected in previous versions. To detect these failures, you may want to change the failure condition level. For more information, see Configure FailureConditionLevel Property Settings.
Number of CPU for Enterprise edition is changing to 8 CPU
SQL Server 2008 R2 Enterprise supports a maximum of 8 CPUs. This is different from previous versions of SQL Server.
To continue using more than 8 processors, you must upgrade to SQL Server 2008 R2 Datacenter.
If you choose to upgrade to SQL Server 2008 R2 Enterprise, SQL Server uses a maximum of 8 processors.
For more information, see, Features Supported by the Editions of SQL Server 2012.
SQL Server Native Client
SQL Server 2008 includes SQL Server Native Client 10.0. For more information about differences in behavior between this version and earlier versions of SQL Server Native Client, see Updating an Application to SQL Server 2008 Native Client from SQL Server 2005 Native Client.