Thank you Dasjo02, you was right.
I'm still having a doubt:
when I create a new token with the same client/resource combination, I want to wait 15 minutes before the complete erasing of the token.
As I read in the Configure Token Lifetime Properties page, I tried to set the "oauth2_access_token_lifetime_sec" variable in #OTK Token Lifetime Configuration but, when I create the second token, the first immediately disappear.
Is that the right variable?
Thank you for your help,
Andrea