Object Journaling is a built-in feature of the IBM i OS. When enabled, it allows you to capture and report on detailed information about file changes. It is a powerful tool for meeting most audit requirements.
Journals were initially built into the OS to provide check points on file updates. You could set a check point before starting a series of updates on one or more files. If the process reached a point where the update could not continue, you could ask the OS to roll back the contents of all files updated so far by your job.
Then, when remote mirroring came along, these journals provided just the right vehicle in the OS to support that process. When a database file is journaled, the journal captures a picture of each record before it is updated and (optionally) again after the update has been processed. With this capability we can look at every database change before it was changed and after it was changed to capture on a field by field basis what was changed. The journal also captures additional information like who did the update, what program was used, the IP address of the interactive session (if applicable), the date and time of the change and more.