Another clue.
With a command "omnimm -list_pool -detail" i have thi output:
Pool name : DAILY_BCK_0_2.0-sp4
Pool Description : Backup GFS Snodo giorni pari
Media type : LTO-Ultrium
Policy : App+Loose
Blocks used [MB] : -2147483648
Blocks total [MB] : -2147483648
Altogether media : 3
Poor media : 1
Fair media : 0
Medium age limit : 36 months
Maximum overwrites : 250
Magazine support : No
Free pool support : None
Pool name : DAILY_BCK_1_2.0-sp4
Pool Description : Backup GFS Snodo giorni dispari
Media type : LTO-Ultrium
Policy : App+Loose
Blocks used [MB] : -2147483648
Blocks total [MB] : -2147483648
Altogether media : 3
Poor media : 1
Fair media : 0
Medium age limit : 36 months
Maximum overwrites : 250
Magazine support : No
Free pool support : None
Why "Blocks used" and "Blocks total" are negative? They should not be positive?