Auditing database on Oracle 9i

Information that can be audited:
- Operating system login user name
- User name
- Session identifier
- Terminal identifier
- Name of the schema object accessed
- Operation performed or attempted
- Completion code of the operation
- Date and time stamp

Step for activating auditing:
1. Activate auditing in initialization paramaters (DB or OS)
audit_trail = DB
2. Activate auditing option
AUDIT SELECT TABLE, UPDATE TABLE, INSERT TABLE, DELETE TABLE BY user_id BY ACCESS;

Here is VIEW to view audit data on database:
- DBA_AUDIT_EXISTS
- DBA_AUDIT_OBJECT
- DBA_AUDIT_SESSION
- DBA_AUDIT_STATEMENT
- DBA_AUDIT_TRAIL
- DBA_OBJ_AUDIT_OPTS
- DBA_PRIV_AUDIT_OPTS
- DBA_STMT_AUDIT_OPTS

reff:http://download.oracle.com/docs/cd/B10501_01/server.920/a96521/audit.htm#1108