Microsoft Office Tutorials and References
In Depth Information
Connecting to Data
In addition, some drivers require special steps for installation on a server. For example, the Oracle
drivers might require granting special permissions to certain registry keys. Read the relevant support
documentation and Knowledge Base articles for those drivers.
Finding a Trusted Provider
To determine whether or not a provider can be trusted, find out the following information from the
manufacturer of the driver or from a dependable source:
Security — Can the provider be trusted to handle security and authentication properly? For
example, verify that the driver cannot be used to launch an attack against Excel Services or the
external data source, and that it respects the privacy of the users (such as handling passwords
and not revealing the queries of one user to other users).
Reliability — Is the provider designed and tested to work reliably in a multithreaded
environment? Some drivers are designed to work in a single-threaded client environment, and might
crash, deadlock, or return incorrect results in multithreaded environments. You should also
verify that the driver can run in unattended mode (for example, it will not launch any UI
when it fails or needs additional information).
Performance — Does the driver provide the performance that is required for your application?
Look at aspects such as running multiple queries in parallel, driver memory consumption,
caching of data, network resources consumption, and running queries asynchronously.
Features — Excel Services takes advantage of certain features of the drivers if they exist. These
are the types of authentication (such as passing the username and password on the connection
string), the ability to define a timeout for the connection, and the ability to cancel the connection
when the request is cancelled or times out.
Because external data drivers run as part of the ECS process, any security, reliability, or performance
issues that the driver might have can impact the whole ECS. Therefore, be very careful when deciding
which drivers can be trusted.
Many BI and other scenarios use SQL Server Analysis Services. Analysis Services 9.0 is the latest version,
but many deployments still use the Analysis Services 8.0 (MSOLAP.2) version.
The MSOLAP.2 driver is in the list of trusted data providers, but it has a number of important limitations
when used with Excel Services:
It does not support 64-bit systems. It can be used only on 32-bit systems.
It does not efficiently support multiple locales from the same ECS process. This has limitations
in multinational companies that use different regional settings against one ECS and one Analysis
It does not support PivotTable grouping.