If you run Nac Manager (legacy java application) then you can delete them quite easily as all of them will be on the same list.
There is also setting for how long should the inactive endsystem be in the database. You can define when will the endsystem table cleanup happen.
![03aca2d0065b4115a4932dd3492c14af_RackMultipart20170110-106252-uw4exh-retention_inline.png 03aca2d0065b4115a4932dd3492c14af_RackMultipart20170110-106252-uw4exh-retention_inline.png](/t5/image/serverpage/image-id/2250i2EFF3D452D74E819/image-size/large?v=v2&px=999)
I am sure the setting is also available in OneView.
Regards
Zdeněk Pala