xascendsessionsvrkey (data too long) in freeradius 2.2.5

I installed freeradius 2.2.5 and i have problem with acounting Error: [sql] Couldn't insert SQL accounting START record - Data too long for column 'xascendsessionsvrkey' at row 1 i can't alter radacct table because i have more than 20 million records I try to use freeradius with test database after alter xascendsessionsvrkey to varchaer(255) the value of xascendsessionsvrkey like ===> 3134:4235:3936::/57 ip v6 disable on radius and database server