Server Architecture and Command Execution - Microsoft SQL Server 2008 Analysis Services - page 479

in its previous state; subsequent commands work with the old version of the object. For a
command that works with multiple properties of an object, at the command's completion
either all the properties are changed or all of them remain the same.

Analysis Services uses the mechanism of transactions to support this atomic behavior. A
transaction is an undividable list of commands that must fully execute or not execute at
all. The transaction mechanism helps maintain the integrity of the system and prevents
the concurrent execution of commands from driving the server into an inconsistent state.
A user can initiate an explicit transaction on the session or the server starts an implicit
transaction for each request. If the server starts an implicit transaction to execute a
request, the server commits the transaction when execution is complete. If the execution
completes successfully, the server makes the changes permanent; if the command fails, the
server rolls back the transaction.

Executing Commands That Change Analysis
Services Objects

Analysis Services uses an XML-based data definition language, within XML/A commands,
to create, delete, and update its objects. The syntax of the Data Definition Language (DDL)
depends heavily on the definition of the objects used in the conceptual data model. Data
management commands usually contain three parts:

. A reference to the object with which the command operates

. A DDL definition of the object

. The parameters used to execute the command

The reference to the object usually contains the identifier for that object, and a list of the
identifiers for its parent objects. (The list can contain identifiers in no particular order.)

You can use data definition commands only with major objects. (See Chapter 4, “The
Conceptual Data Model,” for more information about major and minor objects.)
Therefore, object references refer only to major objects. Listing 26.1 shows a reference of
the Sales measure group object.

LISTING 26.1

Reference Section of a Command That Operates on the Sales Measure Group

<DatabaseID>Foodmart 2008</DatabaseID>
<CubeID>Warehouse and Sales</CubeID>
<MeasureGroupID>Sales</MeasureGroupID>

All the data definition commands have a lot in common, but each command has its own
set of parameters. We'll examine the most important data definition commands: Create ,
Alter , Delete , and Process .