Unlock User Monitoring/Auditing

Hi All,

We have huge list of end users who uses the application to login , their user accounts get locked based on password verify fuctionality within database.

We have many DBAs in our team, who login to database with their id and unlcok the specific user account.

We would like to trace the history of all user account is unlocked by specific DBAs. I believe, this can be achieved by Audit, however i wonder whether we have any base tables/views available which trace these details by default without audit enabled?

Can somebody throw some light on this?

Appreciate, if you could provide complete details with steps how to trace with v$views/base table or audit option.