Few days ago, I told one of my friends that the XMLTYPE column equals to CLOB type, that is not true, it's an object type. Later he ask me how to modify the cache property of XMLTYPE column, I had no idea of this data type, the first thing I did was describe the XMLTYPE object.
SQL> DESC XMLTYPE
METHOD
------
STATIC FUNCTION CREATEXML RETURNS XMLTYPE
Argument Name Type In/Out Default?
---------------- ------- ------ --------
XMLDATA CLOB IN
......
I found that almost every member functions has a parameter called "XMLDATA", then I make suggestion to treat the "column.XMLDATA" as a CLOB object. Later I test it in a test database, found that my suggestion is absolutely correct.
SQL> create table t_xmltype (col1 xmltype);
Table created.
SQL> ALTER TABLE T_XMLTYPE MODIFY LOB (COL1.XMLDATA) (CACHE);
Table altered.
Then I told he to read more books, which will enable people find out the final solution.