Which is better - BLOB, CLOB or XMLTYPE?

Question

Hi All,
We have to store XML in one of the fields in our table.
XML size is not fix but its not so huge that we shold go for external LOBs.
I mean it will be alwas less than 4G.
Our concern here is, does CLOB allocates exactly as much memory needed as much the data is present,(something like VARCHAR2).
How is it in case of BLOB and XMLTYPE as well?
Is there any Oracle documentation or way (code snippet) to verify this?
Thanks in advnace.
Avinash.

Answer 1

You have asked if CLOB allocates space like VARCHAR2 - yes it does. Maybe this example will be better:
SQL> TRUNCATE TABLE test_table;
Tabela zosta│a obciŕta.
SQL> insert into test_table values(LPAD('A', 100, 'A'));
1 wiersz zosta│ utworzony.
SQL> insert into test_table values(LPAD('A', 1000, 'A'));
1 wiersz zosta│ utworzony.
SQL> insert into test_table values(LPAD('A', 10000, 'A'));
1 wiersz zosta│ utworzony.
SQL> COMMIT;
Zatwierdzanie zosta│o uko˝czone.
SQL> SELECT LENGTH(col1) FROM test_table;
LENGTH(COL1)
         100
        1000
        4000
SQL>