SQL> create table t1 ( c1 long );

Table created.

SQL> create table t2 ( c2 long raw);

Table created.

SQL>
SQL> exec   insert into t1 values ('xxxxxx');

PL/SQL procedure successfully completed.

SQL> exec   insert into t2 values ( hextoraw('FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF'));

PL/SQL procedure successfully completed.

SQL>
SQL> commit;

Commit complete.

SQL>
SQL> alter table t1 modify c1 clob;

Table altered.

SQL> alter table t2 modify c2 blob;

Table altered.

SQL> select * from t1;

C1
----------------------------------------------------------------------------------------------------------------------------------
xxxxxx

1 row selected.

SQL> select * from t2;

C2
----------------------------------------------------------------------------------------------------------------------------------
FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF

1 row selected.

SQL>