Thanks very much Jeff, I´m collecting this structure since a month or more in order not to drop indexes used in less frecuently reports. About DES reuse not at all I monitor it with monitorconfig.
I update my indexes statistics getting dml change output and I do reorgs looking after derived stats. So I don´t think that may be a not used table cached by a maintenance operation, but I will check it anyway.
So, the only doubt I have right now its about tables not used. I understand your point about Operations = 0 in IndexID = 0 if it is in memory, it was used by someone without any doubt . The "not collected tables" (in a long period not to drop report´s tables) approch for this may be better in this situation?
Thanks.
Javier Barthe.