Difference between DFM,Operations Manager,On command System Manager
DFM was the original product name for the central management product to monitor multiple NetApp storage systems. With version 4.0, DFM was rebranded to be known as Operations Manager. Starting with version 5.0, the NetApp Management Tools were rebranded to be the OnCommand suite of products. The product formerly called DFM/Operations Manager is now called OnCommand Unified Manager Core. There are other products under the OnCommand product banner: OnCommand Insight was formerly called SANscreen and OnCommand Balance was formerly called BalancePoint. The purpose of OnCommand Unified Manager Core is the same as it was when the product was called DFM: provide the ability to monitor multiple NetApp storage systems from a centralized place.
As far as OnCommand System Manager, OnCommand System Manager (a.k.a. System Manager) is the replacement management tool for FilerView. FilerView was the GUI for managing individual NetApp storage systems. System Manager was introduced around the Data ONTAP 7.3 release to be a comprehensive GUI management tool for NetApp storage systems. With FilerView, there was a specific URL for each NetApp storage system that was used to connect to the management GUI. This wasn't a problem if you had a few NetApp storage systems in your environment, but having to keep track of the FilerView URL become a challenge if your NetApp storage systems grew in numbers. With System Manager, you can manage all of your NetApp storage systems from a centralized interface. Starting with Data ONTAP 8.1, FilerView is no longer available and the only GUI management tool for NetApp storage systems running Data ONTAP 8.1 or above is System Manager.
In summary, OnCommand is the overall brand name for the NetApp management suite of products. OnCommand Unified Manager Core is the new name for what was once called DFM & Operations Manager and is your centralized tool to monitor NetApp storage systems. OnCommand System Manager is the replacement for FilerView and is the centralized tool to manage NetApp storage systems.