With the first release of Oracle9i Database, when you stored an instance of the XMLType datatype, the underlying storage model was a CLOB value. The entire document was read and stored as-is in a CLOB object in the database.
CREATE TABLE "SCOTT"."T"
( "X" "SCOTT"."XMLTYPE"
) PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS NOLOGGING
STORAGE(INITIAL 131072 NEXT 131072 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT)
TABLESPACE "TOOLS"
XMLTYPE COLUMN "X" STORE AS CLOB (
TABLESPACE "TOOLS" ENABLE STORAGE IN ROW CHUNK 8192 PCTVERSION 10
NOCACHE NOLOGGING
STORAGE(INITIAL 131072 NEXT 131072 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT))
scott@10GR2> create table t_xmlclobs(x clob);
Table created.
scott@10GR2> create table t_xmltype (x xmltype);
Table created.
scott@10GR2> declare
2 l_start_time number;
3 begin
4 l_start_time := dbms_utility.get_time;
5 for i in 1..10000
6 loop
7 insert into t_xmlclobs(x) values ('
8 end loop;
9 commit;
10
11 dbms_output.put_line(' Total Time for Clobs='|| ( dbms_utility.get_time - l_start_time) );
12
13 l_start_time := dbms_utility.get_time;
14 for i in 1..10000
15 loop
16 insert into t_xmltype(x) values ('
17 end loop;
18 commit;
19
20 dbms_output.put_line(' Total Time for Xmltype ='|| ( dbms_utility.get_time - l_start_time) );
21 end;
22 /
Total Time for Clobs = 42
Total Time for Xmltype = 1641
PL/SQL procedure successfully completed.
When an XMLType instance is created, an XML syntax check is performed—regardless of the storage architecture—to ensure that the XML document is well formed.
