Determine (again) the places to store the dot position

Although we discussed the place to store the dot position (e.g. discussion related with INFRA-207), we re-visited this topic after the November run.
So far, dot position is stored under pfs_instdata, and the latest data contains spotId, x, y position in mm, and dot radius in mm.

I personally think the dot position should be stored on pfs_insdata for netflow/ETS.
What I think we need to discuss is whether we should store the information on opDB (and its schema). Considering that FF positions are stored on opDB as well as pfs_insdata, it should be stored on opDB for cobra movement. 

The data format on pfs_instdata should also be discussed... By the way, does spotId synchronize with cobraId?