Product:
Cognos BI 8.4.1
Windows 2008 R2 server
Microsoft SQL server 2005

Symptom:
Error during start of cognos service from cognos configuration.
EventService StartService Failure

This is on a second Cognos BI report server installed to add to a existing Cognos BI server installation to get more report processing power.

If you run a test from inside cognos configuration you get error like this:
Testing the database connection
No JDBC driver could be found in classpath
com.ibm.db2.jcc.DB2Driver

Error message:
In the cogserver.log file you will find errors like these;
CNC-SDS-0256 Unable to connect to the database using jdbc.db2.com
DPR-DPR-1035 Dispatcher detected an error
problem initializing handler monitorServiceHandler
CNC-SDS-0322 Database update failed with error code ACCESS_FAILURE_UNKNOWN.
The JSM service will be aborted.

Cause:
The default configuration for Cognos is to use DB2, you need to change the notification store to be using SQL server.

The Event service need access to the content store database.

Solution:
Go to Cognos Configuration
Go to Data Access – Notification
Right click on Notification store and select Delete
Right click on Notification and select New Resource – Database
Enter name Notification store
Select Microsoft SQL Server database
Enter database server and port number to be the same as content store connection on first Cognos BI server.
Enter user id and password to access content store database
Enter Database name to be same as content store name.
Go to top in cognos configuration
Click on save
Click on start the cognos bi service.