SQL Error: cannot update read-only view CUST_ADD

Hello,

I try to update a field in a SQL Database, but I receive a Error description
"cannot update read-only view CUST_ADD"!
How can I change the access or how can I update this field?

select * from cust_add  where VC_address_1 = 'Nauenstrasse 49' AND I_Cust =
'1'; => this work!

But this doesn't work: update cust_add set VC_address_1 = 'Hochstrasse 39'
where VC_address_1 = 'Nauenstrasse 49' AND I_Cust = '1';
Error description: -150 => cannot update read-only view CUST_ADD

If anywhere know, how I can change this, please send me a Mail

Regards  Pascal Wenger