Follw the next steps to turn on Auditing in Cognos Administration.
1. Open Cognos Configuration
2. Right-click on Logging and from the popup menu select New Resource->Destination.
3. Name the new resource Audit, and leave the type as Database, then click OK.
4. Right-click on the resource Audit, and from the popup menu select New Resource->Database.
5. Name the database resource, and change the type to, then click OK.
6. Select the database above, and enter the database details
7. Right-click on Audit, and from the popup menu select Test.
8. If the Audit database test is successful then click Close, else click Details and investigate the problem.
9. Now restart your cognos server.
1. Login to the Cognos Server with an Administrator Account
2. Select Administer Cognos Content
3. From the small menu on the left select System
4. From the Lower Right panel select Set Properties
5. Select the Category Logging, change all values to Basic, and select the boxes Audit the native query for batch report service and Audit the native query for report service
Also find more on the IBM website here
In the same article someone noted that there have been no changes in Cognos 10 regarding Auditing.