Which of the following tasks is NOT part of Historian Maintenance?

The task of deleting a folder is not part of Historian Maintenance. Historian Maintenance typically focuses on preserving data integrity and ensuring the smooth operation of the system. This includes activities like backing up historian data and configuration, which are essential for recovery and continuity in case of system failure or data loss. Restoring a history block is also critical as it pertains to retrieving previous data states when needed.

In contrast, deleting a folder does not contribute to the maintenance or preservation of the historian's data or configuration. Instead, it could potentially lead to data loss or system issues, making it an action that falls outside the scope of standard maintenance tasks aimed at ensuring the reliability and accessibility of historian records.