如果数据太大，我们无法对clob变量直接赋值，这时我们可以通过dbms_lob.read、dbms_lob.write方法分阶段的读取和写入clob变量内。但这时我们应该对clob变量建立缓存，如下的第一句。这里给出一个示例程序，可以通过变换dbms_lob.read和dbms_lob.write顺序使程序不仅能写入大数据还能读取大数据。
dbms_lob.createtemporary(lob_loc => x_clob,
cache => TRUE);
PROCEDURE load_clob(p_clob_in IN CLOB,
x_clob IN OUT NOCOPY CLOB) IS
l_clob_len NUMBER := dbms_lob.getlength(p_clob_in);
l_data VARCHAR2(32756);
l_buf_len_std NUMBER := 4000;
l_buf_len_cur NUMBER;
l_seg_count NUMBER;
l_write_offset NUMBER;
BEGIN
IF p_clob_in IS NOT NULL THEN
l_seg_count := floor(l_clob_len / l_buf_len_std);
FOR i IN 0 .. l_seg_count
LOOP
IF i = l_seg_count THEN
l_buf_len_cur := l_clob_len - i * l_buf_len_std;
ELSE
l_buf_len_cur := l_buf_len_std;
END IF;
IF l_buf_len_cur > 0 THEN
dbms_lob.read(lob_loc => p_clob_in,
amount => l_buf_len_cur,
offset => i * l_buf_len_std + 1,
buffer => l_data);
l_write_offset := nvl(dbms_lob.getlength(lob_loc => x_clob),
0) + 1;
dbms_lob.write(lob_loc => x_clob,
amount => l_buf_len_cur,
offset => l_write_offset,
buffer => l_data);
END IF;
END LOOP;
END IF;
END load_clob;