Audit logging is one of many important administrative features available with IBM Cognos BI. However, it tends to confuse ibm cognos administrators with various levels and tables it has for it. For ibm cognos 10.1 (it applies the same to ibm cognos 8 except the grey ones), there's a chapter available in redbook for understanding Cognos Audit Logging.
The redbook (page 503 onward/ Chapter 10.5 Auditing), lists setting up audit db, various audit tables and their definitions and the effect each audit logging level would have in general sense. Although, this definition and effect of levels is generalized in Cognos environment sense, you could set up audit logging higher for a particular component to audit its usage.
Audit database table definitions
The redbook (page 503 onward/ Chapter 10.5 Auditing), lists setting up audit db, various audit tables and their definitions and the effect each audit logging level would have in general sense. Although, this definition and effect of levels is generalized in Cognos environment sense, you could set up audit logging higher for a particular component to audit its usage.
Audit database table definitions
IBM Cognos audit and logging levels