Log Analysis can be used to determine the following:


To check what a target user has accessed while using salesforce.com or information related to changes made to a specific record via the user interface. The following changes can be tracked during the users logged in session:

Record’s created, viewed, edited, updated and deleted

The information provided in the logs will not contain the old and new values of the record. Any record modified via an API will not be tracked. Examples of this would be: API integrations, applications, and Custom Apex queries.

Check the below link for detailed information

https://help.salesforce.com/apex/HTViewSolution?id=000212606&language=en_US

Cheers!!!