How does oracle write to datafiles in a tablespace?

Question

hi all
Suppose I have a tablespace consisting of two datafiles. When I need to wirte data onto it，how does ORACLE
write ? Does it initially write to the first datafile and then write to the second datafile when the first datafile getting full or write to two datafiles in an random manner?
Thanks for your reply.

Answer 1

hi all
I have read reply in reponse to thread "tablespaces or datafile " and testcase in that thread shows that ORACLE will write to datafiles in round-robin manner.
But my test show totally different result:
SQL>
SQL> create tablespace ts_maoxl
2 datafile '/crash/oradata/TESTDB/datafile/1.bdf' size 5m,
3 '/crash/oradata/TESTDB/datafile/2.bdf' size 5m
4 EXTENT MANAGEMENT LOCAL;
Tablespace created
SQL>
SQL> create table maoxl(id char(2000),id3 char(2000),id2 char(2000)) tablespace ts_maoxl;
Table created
SQL>
SQL> declare
2 begin
3 for i in 0..99 loop
4 insert into maoxl values('x','y','z');
5 end loop;
6 commit;
7 end;
8 /
PL/SQL procedure successfully completed
SQL> select count(*) from maoxl;
COUNT(*)
100
SQL> select t.file_id,t.extent_id,bytes from dba_extents t where tablespace_name='TS_MAOXL';
FILE_ID EXTENT_ID BYTES
5 0 65536
5 1 65536
5 2 65536
5 3 65536
5 4 65536
5 5 65536
5 6 65536
5 7 65536
5 8 65536
5 9 65536
5 10 65536
5 11 65536
5 12 65536
5 13 65536
14 rows selectedAll extents are allocated from datafile 5,none from datafile 6. My result is different from yours.
BTW,The result of my testcase was from a 10.2.0.4 database running on HP-UNIX
What could be the problem?
thanks