Microsoft Office Tutorials and References
In Depth Information
Connecting to Data
DCL Only — The ECS will first check that the connection file path the workbook contains points to
a trusted DCL, and will try to load and use the connection from that file. If it fails to load the file
from the DCL, the ECS will return an error to the user, and will not try to use the embedded
connection information. Using the DCL Only value ensures that only trusted connections will be used
by Excel Services and is best from a security point of view. However, it does have a performance
impact, because the ECS will need to download the connection file from the SharePoint document
library.
DCL And Embedded — Excel Services will check the Always Use Connection File flag of the
workbook. If the flag is set, it will try only the DCL connection and ignore the embedded connection.
If the flag is not set, the ECS will first try to connect using the embedded data connection
information, and if that fails, it will fall back to the DCL connection.
Linked Connection Path
As discussed in the previous section, Excel Services may download and use a file from a DCL. The
workbook can contain a path to a DCL file instead of the embedded connection information.
This path is an absolute path. Therefore, you can move or copy the workbook to a different location and
it will continue to work against the same DCL file. On the other hand, moving the connection file from
the DCL will result in the workbook failing to connect (except when using the embedded connection
information).
This becomes a problem if you have one or more data connections and workbooks on a test server and
you want to move them to a production server. The only solution is to update all the workbooks (either
manually or by using script) to use the path to the DCL on the new server.
Trusted Data Providers
Excel Services manages a list of trusted data providers. The ECS only executes queries to data sources
that have been deemed safe and added to this list.
The server is installed with a default list of trusted providers, and the administrator can add or remove
providers from the list. Figure 5-4 shows the administrator page for managing the list of trusted data
providers. By default, the following data providers are supported:
Microsoft SQL Server:
SQLOLEDB and SQLOLEDB.1
SQL Server ODBC and ODBC DSN
SQLNCLI and SQLNCLI.1 OLEDB drivers
SQL Native Client ODBC and ODBC DSN
Microsoft OLAP Services:
MSOLAP
MSOLAP.2 (Microsoft OLE DB Provider for OLAP Services 8.0)
MSOLAP.3 (Microsoft OLE DB Provider for OLAP Services 9.0)
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