Facets

The American Heritage Dictionary of the English Language (Fourth Edition) defines facet as: One of numerous aspects, as of a subject. The definition of Aspect (from the same dictionary) is: Appearance to the eye, especially from a specific vantage point. The definition of Facet in SQL Server Books Online is: A set of logical properties that model the behavior or characteristics for certain types of managed targets. The number and characteristics of the properties are built into the facet and can be added or removed by only the maker of the facet. A target type can implement one or more management facets, and a management facet can be implemented by one or more target types. Some properties of a facet can only apply to a specific version. For example, the Database Mail property of the Surface Area Configuration facet only applies to SQL Server 2005 and later versions.

Though Policy-Based Management relies heavily on facets, they're really concept that goes beyond PBM. When I was a kid I'd get these pictures that had hidden items. To find the items you had to use different pieces of colored translucent paper (like red or green). Just looking at the picture you couldn't see the "hidden" elements. But placing the red sheet over the picture revealed the hidden treasures. Facets are sort of the same way.

Another analogy I've used to describe facets is Internet Explorer. Think back to the early days of IE and you wanted to change the way IE handled ActiveX controls. You'd navigate to Tools -> Options, go to the Advance tab and scroll through a long list of settings. No one every really knew if their browser settings were secure or not. Think of the handling of ActiveX controls as a property of the browser with the values Do not Allow, Prompt, Always Allow. Requiring a user to reason about this, and many other properties, is insane. My mom, for example, has no idea what this means or what the proper setting should be. In IE 5.5 the IE team introduced a security facet. They didn't call it that but that's what it is. They introduced the concept of a Security Level with the values: High, Medium-High, and Medium. Effectively this is a new logical property in IE. I call it a logic property as it has no intrinsic meaning - it doesn't really control anything. Ah, but what it does do is incredibly powerful (yes, I'm contradicting myself). This logical property is really an aggregation of several physical properties (e.g. ActiveX Controls) a proxy for a group of settings. By creating the logical property the administration of IE is greatly simplified. My mom can understand Medium-high security - more importantly I can walk her through the steps to properly configure IE. Facets in SQL Server are very similar concept.

Take Database, for example. There are lots of physical properties for a database: Name, Collation, Compatibility Level, Auto Close, Encryption Enabled, Log File location, Data File Location, etc. In fact, a database has something like 60 properties. Wow, how does one reason about 60 properties? The facet allows us to do three powerful things: 1) create a single view of all of the physical properties for a database, 2) create specific views of database properties; for example, security, compliance, performance, etc and 3) create logical properties which are derived from one or more physical properties. There was a key point I just introduced: facets are over objects (target types) in the system and an object (target type) can have more than one facet. Databases, tables, views, logins, can have facets. in SQL Server 2008 we didn't cover every object (target type). For example, we didn't cover Replication, Agent, or DB Mail. But more on that later. So just think of a facet as a collection of related properties for a given object or similar set of objects.

The implementation of a facet is .Net code - for us it's C#. In SQL Server 2008 users cannot create their own facets, although we designed the system with extensibility in mind.

Let's take a closer look at how facets are exposed in the Management Studio. There are two ways to look at a facet: 1) the facet definition and 2) an object (target type) with respect to a particular facet.

Facet Definition

The facet definitions, meaning the description and properties that make up the facet, can be found in OE. See the picture below.

Right-Clicking any facet and selecting Properties displays the Facet Properties dialog. In this dialog you'll get a description of the facet, the target types it applies to and a list of all of the properties (with description) that make up the facet. The sample below is for the Database facet.

This covers the first view of facets: the facet definition. Now let's look at viewing a particular target in the context of a facet. The screen shot below shows the context menu for a database.

Look about halfway down the context menu and you'll see menu item called Facets. Selecting this menu item launches the Facet dialog for database. The screen shot below shows the dialog for the AdventureWorks sample database.

The Facet combo box is expanded. This allows you to choose which facet you want to view for the selected object. Only the facets that apply to the selected object type are displayed. In this screen shot the Database facet is selected. This shows you all of the properties on a database and the current value for each property for the selected database.

Two other key things to point out: 1) You'll notice that some properties are bold while others are grayed out. The bolded properties are read/write and can be updated; the grayed out properties are read-only. This means, instead of going to the standard Database properties dialog you can come here and change a database property. 2) You'll notice the button in the bottom right labeled Export Current State as Policy... ". Let's suppose you've configured the database exactly as you like it but you want a create a policy that monitors any changes from the original state. This option creates a policy and condition for the selected facet using for the current state. It's a very nice shortcut for creating policies, saving you a bunch of time typing in properties and values.

The final thing a facet does is define the supported evaluation modes for policies. All facets for the Database Engine can be checked on schedule. Check on Change: Prevent and Check on Change: Log depend upon the eventing model of the Database Engine. Because the supported evaluation modes are on the facet all of the properties in the facet must support support the same set of events. This means for a facet to support Check on Change: Prevent all of the properties in the facet must raise a DDL event.

The three tables below are a great reference to print out and keep handy when using PBM.

This table maps each facet to the supported evaluation mode(s):

Facet Name	CoC: Prevent	CoC: Log	CoS
Application Role	X	X	X
Asymmetric Key	X	X	X
Audit			X
Backup Device			X
Broker Priority			X
Broker Service			X
Certificate			X
Credential			X
Cryptographic Provider			X
Data File			X
Database			X
Database Audit Specification			X
Database Ddl Trigger			X
Database Maintenance			X
Database Option		X	X
Database Performance			X
Database Role	X	X	X
Database Security			X
Default			X
Endpoint	X	X	X
File Group			X
Full Text Catalog			X
Full Text Index			X
Full Text Stop List			X
Index			X
Linked Server			X
Log File			X
Login			X
Login Options	X	X	X
Message Type			X
Multipart Name	X	X	X
Name			X
Partition Function			X
Partition Scheme			X
Plan Guide			X
Remote Service Binding			X
Resource Governor			X
Resource Pool	X	X	X
Rule			X
Schema	X	X	X
Server			X
Server Audit			X
Server Audit Specification			X
Server Configuration		X	X
Server Ddl Trigger			X
Server Information			X
Server Performance			X
Server Security			X
Server Settings			X
Server Setup			X
Service Contract			X
Service Queue			X
Service Route			X
Statistic			X
Stored Procedure	X	X	X
Surface Area		X	X
Surface Area for AS
Surface Area for RS
Symmetric Key			X
Synonym			X
Table			X
Table Options	X	X	X
Trigger			X
User			X
User Defined Aggregate			X
User Defined Data Type			X
User Defined Function	X	X	X
User Defined Table Type			X
User Defined Type			X
User Options	X	X	X
View			X
View Options	X	X	X
Workload Group	X	X	X
Xml Schema Collection			X

The tables below map the relationship between Facets and Target Types. The table on the left shows the facets for each target type. The table on the right shows the target types supported by each facets.

Facets by Target Type		Target Types by Facet
ANALYSIS SERVICES		Application Role
Surface Area for AS		APPLICATION ROLE
APPLICATION ROLE		Asymmetric Key
Application Role		ASYMMETRIC KEY
Name		Audit
ASYMMETRIC KEY		AUDIT
Asymmetric Key		Backup Device
Name		BACKUP DEVICE
ASYMMETRIC KEY USER		Broker Priority
User Options		BROKER PRIORITY
AUDIT		Broker Service
Audit		BROKER SERVICE
BACKUP DEVICE		Certificate
Backup Device		CERTIFICATE
BROKER PRIORITY		Credential
Broker Priority		CREDENTIAL
BROKER SERVICE		Cryptographic Provider
Broker Service		CRYPTOGRAPHIC PROVIDER
CERTIFICATE		Data File
Certificate		DATA FILE
Name		Database
CERTIFICATE USER		DATABASE
User Options		Database Audit Specification
CREDENTIAL		DATABASE AUDIT SPECIFICATION
Credential		Database Ddl Trigger
CRYPTOGRAPHIC PROVIDER		DATABASE DDL TRIGGER
Cryptographic Provider		Database Maintenance
DATA FILE		DATABASE
Data File		Database Options
DATABASE		DATABASE
Database		Database Performance
Database Maintenance		DATABASE
Database Options		Database Role
Database Performance		ROLE
Database Security		Database Security
DATABASE AUDIT SPECIFICATION		DATABASE
Database Audit Specification		Default
DATABASE DDL TRIGGER		DEFAULT
Database Ddl Trigger		Endpoint
DATABASE ROLE		ENDPOINT
Name		File Group
DEFAULT		FILE GROUP
Default		Full Text Catalog
Name		FULL TEXT CATALOG
ENDPOINT		Full Text Index
Endpoint		FULL TEXT INDEX
FILE GROUP		Full Text Stop List
File Group		FULL TEXT STOP LIST
FULL TEXT CATALOG		Index
Full Text Catalog		INDEX
FULL TEXT INDEX		Linked Server
Full Text Index		LINKED SERVER
FULL TEXT STOP LIST		Log File
Full Text Stop List		LOG FILE
FUNCTION		Login
Multipart Name		LOGIN
User Defined Function		Login Options
GROUP USER		LOGIN
User Options		Message Type
INDEX		MESSAGE TYPE
Index		Multipart Name
Name		FUNCTION
LINKED SERVER		PROCEDURE
Linked Server		SYNONYM
LOG FILE		TABLE
Log File		TYPE
LOGIN		VIEW
Login		XML SCHEMA COLLECTION
Login Options		Name
MESSAGE TYPE		APPLICATION ROLE
Message Type		ASYMMETRIC KEY
PARTITION FUNCTION		CERTIFICATE
Partition Function		DATABASE ROLE
PARTITION SCHEME		DEFAULT
Partition Scheme		INDEX
PLAN GUIDE		RULE
Plan Guide		SCHEMA
PROCEDURE		SQL ASSEMBLY
Multipart Name		STORED PROCEDURE
Stored Procedure		SYMMETRIC KEY
REMOTE SERVICE BINDING		SYNONYM
Remote Service Binding		TABLE
REPORTING SERVICES		TRIGGER
Surface Area for RS		USER
RESOURCE GOVENOR		USER DEFINED FUNCTION
Resource Governor		USER DEFINED TYPE
RESOURCE POOL		VIEW
Resource Pool		XML SCHEMA COLLECTION
ROLE		Partition Function
Database Role		PARTITION FUNCTION
RULE		Partition Scheme
Name		PARTITION SCHEME
Rule		Plan Guide
SCHEMA		PLAN GUIDE
Name		Remote Service Binding
Schema		REMOTE SERVICE BINDING
SERVER		Resource Governor
Server		RESOURCE GOVENOR
Server Configuration		Resource Pool
Server Information		RESOURCE POOL
Server Performance		Rule
Server Security		RULE
Server Settings		Schema
Server Setup		SCHEMA
Surface Area		Server
SERVER AUDIT		SERVER
Server Audit		Server Audit
SERVER AUDIT SPECIFICATION		SERVER AUDIT
Server Audit Specification		Server Audit Specification
SERVER DLL TRIGGER		SERVER AUDIT SPECIFICATION
Server Ddl Trigger		Server Configuration
SERVICE CONTRACT		SERVER
Service Contract		Server Ddl Trigger
SERVICE QUEUE		SERVER DLL TRIGGER
Service Queue		Server Information
SERVICE ROUTE		SERVER
Service Route		Server Performance
SQL ASSEMBLY		SERVER
Name		Server Security
SQL USER		SERVER
User Options		Server Settings
STATISTIC		SERVER
Statistic		Server Setup
STORED PROCEDURE		SERVER
Name		Service Contract
SYMMETRIC KEY		SERVICE CONTRACT
Name		Service Queue
Symmetric Key		SERVICE QUEUE
SYNONYM		Service Route
Multipart Name		SERVICE ROUTE
Name		Statistic
Synonym		STATISTIC
TABLE		Stored Procedure
Multipart Name		PROCEDURE
Name		Surface Area
Table		SERVER
Table Options		Surface Area for AS
TRIGGER		ANALYSIS SERVICES
Name		Surface Area for RS
Trigger		REPORTING SERVICES
TYPE		Symmetric Key
Multipart Name		SYMMETRIC KEY
USER		Synonym
Name		SYNONYM
User		Table
USER DEFINED AGGREGATE		TABLE
User Defined Aggregate		Table Options
USER DEFINED DATA TYPE		TABLE
User Defined Data Type		Trigger
USER DEFINED FUNCTION		TRIGGER
Name		User
USER DEFINED TABLE TYPE		USER
User Defined Table Type		User Defined Aggregate
USER DEFINED TYPE		USER DEFINED AGGREGATE
Name		User Defined Data Type
User Defined Type		USER DEFINED DATA TYPE
VIEW		User Defined Function
Multipart Name		FUNCTION
Name		User Defined Table Type
View		USER DEFINED TABLE TYPE
View Options		User Defined Type
WINDOWS USER		USER DEFINED TYPE
User Options		User Options
WORKLOAD GROUP		ASYMMETRIC KEY USER
Workload Group		CERTIFICATE USER
XML SCHEMA COLLECTION		GROUP USER
Multipart Name		SQL USER
Name		WINDOWS USER
Xml Schema Collection		View
		VIEW
		View Options
		VIEW
		Workload Group
		WORKLOAD GROUP
		Xml Schema Collection
		XML SCHEMA COLLECTION

 

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About the Author:
Dan Jones is a PM on the SQL Server Manageability team at Microsoft.