The Flexfield is used to group assets by financial or logical identification and usually depreciate using the same rules. Two Segments are predefined in the oracle Appliaction Major category and Minor category and frequently they are used & to group assets by non-financial information. In my little experience there is no use for this flexfiled . Although we have to create at least on segment with a default value in its value set because they asset key field on the asset addition window will become mandatory.
This video demonstrates How to Manage Fixed Assets Flexfield in Fusion Financials Cloud:
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