Server Architecture and Command Execution - Microsoft SQL Server 2008 Analysis Services - page 486

The syntax for these commands is simple:

<BeginTransaction/>
<CommitTransaction/>
<RollbackTransaction/>

When Analysis Services receives a BeginTransaction command, it checks whether there is
an existing Transaction object on the current session. If there isn't, Analysis Services
creates a new Transaction object and assigns it a unique identifier. If there is an existing
Transaction object on the current session, Analysis Services increments the internal
counter for that Transaction object. The current version of Analysis Services doesn't
support nested transactions. All subsequent operations execute inside the transaction. A
user (or multiple users) working with different sessions don't see changes occurring inside
the transaction; the changes aren't visible until they are committed. After the transaction
is committed, users can see the updated objects.

You should call the CommitTransaction command as many times as you call the
BeginTransaction command, before the CommitTransaction command commits the
changes. However, if the changes are to be rolled back, the RollbackTransaction
command rolls back the changes no matter how many times BeginTransaction was called
before RollbackTransaction (as shown in Figure 26.3). If you try to roll back a transaction
before it starts, Analysis Services returns an error.

Server

Session Session

Request Request

Begin
Transaction

Begin
Transaction

Begin Transaction Begin Transaction

Command 1 Command 1

Command 2 Command 2

Begin Transaction Begin Transaction

Command 3 Command 3

Command 4 Command 4

Commit Transaction Rollback

Transaction

Commit
Transaction

Command 5

Command 6

Commit
Transaction

Commit Transaction

FIGURE 26.3 If all commands execute successfully, they are committed; if one command in
the transaction fails, they all roll back.