Product:
IBM Cognos BI 10.2.2
Microsoft Windows 2012 R2 Server
Microsoft SQL database 2012 server

Symptom:
When testing a data source, for like Audit database, you get a “logon Failed” after an upgrade to new version of Cognos BI.(where you also have installed on new Windows servers for BI and database.)
You have changed the signon to have the new SQL password to the data source, still you get an error.

If you create a test.udl file and connect with same user and password it works when using the Microsoft OLE DB Provider for SQL server.

Error Message:
Microsoft SQL Server (SQL 2008 Native Client) / Compatible Failed
QE-DEF-0285 The Logon failed.
Microsoft SQL server (JDBC) / Dynamic Succeeded
XQE-DS-0015 getDatabaseProductName: “Microsoft SQL Server”

UDA-SQL-0031 Unable to access the “testDataSourceConnection” database.
UDA-SQL-0534 Invalid connection string.

Solution:
The driver for Microsoft SQL is missing.
Download from Microsoft Web site, and install sqlncli.msi for SQL 2012.

Then you can look into Windows Control panel on server, and check programs, there in the list of installed programs should be;
Microsoft SQL Server 2012 Native Client – Version: 11.2.5058.0

Best if you install both 2005, 2008 and 2012 SQLNCLI files so any old Data connection in Cognos BI will work as is.

If you in Cognos Connection use Microsoft SQL Server (ODBC) instead of Microsoft SQL Server (SQL 2008 Native Client) it will also work. When you use “native client” then it must be installed on the Windows Server for Cognos BI to work.

Download SQL 2008 driver from here:
https://www.microsoft.com/en-us/download/details.aspx?id=44272