I'm using EF6 Code First with Oracle 12c.
I have a property that requires the data max length:
user.Property(u => u.PasswordHash).HasColumnType("NVARCHAR2").IsMaxLength();
PASSWORDHASH = c.String(maxLength: 32767, storeType: "nvarchar2")
when I try to migrate I get:
ORA-00910: specified length too long for its datatype
Extended DataType is enable in my database and I can create the table successfully using a script.
I'm not sure what is below your c# code but 32767 is max length for PL/SQL if this goes with plain SQL limit is 4000. So I think you should change it to 4000.
The limit is in fact 4000 bytes so if you insert 2-byte character it gets less than 4000 chars.