Policy-Based Management

• Policy based system for managing one or more instances of SQL Server
• Create conditions that contain condition expressions. Then, create policies that apply the conditions to database target objects

Facets are used to create conditions, which can then be used to apply to policies

Facet  – group of logical propertie

Condition – A check that is evaluated by a policy

Policy – a conditon that is applied to a given set of target object

Category – A group of policies that help you manage policy enforcement

Target – Object that is being managed by the policy

Administering Servers by Using Policy-Based Management

Policy-Based Management is a system for managing one or more instances of SQL Server 2008. When SQL Server policy administrators use Policy-Based Management, they use SQL Server Management Studio to create policies to manage entities on the server, such as the instance of SQL Server, databases, or other SQL Server objects.

Note: The msdb database contains all the policy definitions, as well as the jobs that execute the policy checks.

Policy-Based Management has three components:

• Policy management –  Policy administrators create policies.
• Explicit administration –  Administrators select one or more managed targets and explicitly check that the targets comply with a specific policy, or explicitly make the targets comply with a policy.
• Evaluation modes – There are four evaluation modes, three of which can be automated:
  • On demand. This mode evaluates the policy when directly specified by the user.
  • On change: prevent. This automated mode uses DDL triggers to prevent policy violations.

    Important

    If the nested triggers server configuration option is disabled, On change: prevent will not work correctly. Policy-Based Management relies on DDL triggers to detect and roll back DDL operations that do not comply with policies that use this evaluation mode. Removing the Policy-Based Management DDL triggers or disabling nest triggers, will cause this evaluation mode to fail or perform unexpectedly.

  • On change: log only. This automated mode uses event notification to evaluate a policy when a relevant change is made.
  • On schedule. This automated mode uses a SQL Server Agent job to periodically evaluate a policy.

  When automated policies are not enabled, Policy-Based Management will not affect system performance.

Source:
http://technet.microsoft.com/en-us/library/bb510667.aspx
Mastering SQL Server 2008 –  By Michael Lee, Gentry Bieker (policy category explaination)