What is Workflow History?
Workflow history in SharePoint is simply a hidden list which contains all of the history and logging from the workflows used within the site. This workflow history list contains the history information including several GUIDs that are used to tie the history item back to the workflow from which it came from.
If your site is running at least one workflow, you should be able to access the workflow history list by using the following URL: http://yoursite/Lists/Workflow%20History/
Why is the Workflow History list in SharePoint practically unreadable?
The reason the workflow history list is practically unreadable is because it is not meant to be read by humans directly. The intended purpose is to store the history during the life cycle of that workflow.
Why is the workflow history deleted?
Technically, the workflow history is not deleted. The association between the workflow (what you see on the workflow status page) and the history list is removed. This is done for performance reasons. Once a workflow is completed, by default the connection between the workflow and the workflow history is deleted after 60 days.
Can I disable the deletion of workflow history?
Yes, although it is not recommended. You can disable the “Workflow Auto Cleanup” timer job if you wish to keep the workflow data. You can read more about that here.
What can I do to help control a massive workflow history list?
When you associate a workflow with a list or library in SharePoint you are asked where you wish to store the Tasks and Workflow History for that workflow. It is common to just accept the defaults and use the same task list and history list for all workflows on a site, however if you have a particular workflow that will have a lot of workflow history, you can simply tell SharePoint to create a separate Workflow History list for this workflow association. This should help balance the load across multiple lists.
What if I want to use the workflow history for auditing?
Microsoft never intended for the workflow history to be used for auditing. One of the reasons is due to security. A savvy user could intentionally or unintentionally make changes to the workflow history since it is a simple list. Changing the security of the Workflow History list can have undesired consequences. The “Best Practice” approach for auditing workflow history would be to use the SharePoint auditing functionality.
How do I use the SharePoint auditing functionality to audit my workflows?
Unfortunately, this auditing report is not available out of the box. However, a custom audit report can be created in Visual Studio in order to extend the auditing functionality to include workflows.