You want to create a user with read only privilege to read the audit events
The customer collector documentation on the SEC_for_Oracle_DB_44.pdf is missing a few permission to grant.
You need to run the following commands:
Username called SSIM_RO is the read only user for the Collector sensor.
CREATE USER SSIM_RO IDENTIFIED BY some_password DEFAULT TABLESPACE some_tablespace TEMPORARY TABLESPACE some_temp_tablespace;
GRANT CONNECT TO SSIM_RO;
GRANT SELECT ON dba_audit_trail TO SSIM_RO;
GRANT SELECT ON sys.aud$ TO SSIM_RO;
GRANT SELECT ON sys.system_privilege_map TO SSIM_RO;
GRANT SELECT ON sys.stmt_audit_option_map TO SSIM_RO;
GRANT SELECT ON sys.audit_actions TO SSIM_RO;
You can also create a group and grant these permission to the group and assign user to this group