Resource Monitoring - Microsoft SQL Server 2008 Analysis Services - page 812

DMVs and SchemaRowset s

Historically speaking, the main resource monitoring application programming interface
(API) for Analysis Services has been Discover XML for Analysis (XML/A) requests (further
discussed in Chapter 32, “XML for Analysis”), also known as SchemaRowset s (a term intro-
duced by an OLE DB specification). The new DMVs are an ad-hoc SQL query-based API
similar to SQL Server relational services DMVs. Before we discuss the benefits of using
DMVs, let's discuss the overall architectural structure of DMVs and the new resource-
monitoring infrastructure, as shown in Figure 41.1.

Analysis Services

SQL

DMVs (DMX layer)
$System schema

SchemaRowsets

XMLA Discover

Client

Resource Monitoring
infrastructure

FIGURE 41.1 Different ways of querying server resources.

As you can see in Figure 41.1, under the hood the DMVs are implemented as a layer on
top of the SchemaRowset infrastructure. DMVs take advantage of a SQL-like query language
that is internally supported by the data-mining parser. After a request to the DMV is sent
to Analysis Services, it is parsed by the data-mining parser, which then generates an inter-
nal SchemaRowset request. The system executes the SchemaRowset request and performs the
necessary post-processing operations such as filtering or sorting.

The new API gives you the power and flexibility of a SQL query language to access system
information. In the past, when executing a SchemaRowset request, you either needed to
write an application (such as the ActivityViewer sample for Analysis Services 2005) or
create a long XML document; DMVs enable you to access the same information by just
typing a query in SQL Server Management Studio. Any other application that invokes the
Analysis Services OLE DB provider or ADOMD.NET provider can query DMVs. Therefore,
you can set up a linked server in SQL Server relational services to expose information
provided by Analysis Services DMVs by querying SQL Server. You can use reporting
services to build reports showing Analysis Services resource consumption and overall
system health.