测试一把

alter session set events '10046 trace name context forever,levle 8';[@more@]

SQL> create table t as select * from dba_objects;

Table created.

SQL> insert into t select * from t;

55867 rows created.

SQL> /

111734 rows created.

SQL> commit;

Commit complete.

SQL> /

Commit complete.

SQL> insert into t select * from t;

223468 rows created.

SQL> commit;

Commit complete.

SQL> show parameter db_file_mult

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_file_multiblock_read_count integer 16
SQL> alter session set events '10046 trace name context forever,level 8';

Session altered.

SQL> alter session set db_file_multiblock_read_count=256;

Session altered.

SQL> select count(*) from t;

COUNT(*)
----------
446936

SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - Production
With the Partitioning, OLAP and Data Mining options
[oracle@tsdb01-shcd ~]$ cd /u01/app/oracle/admin/southdb/udump/
[oracle@tsdb01-shcd udump]$ ls
southdb_ora_19628.trc

查看相应的trace文件,里面应有如下('db file scattered read)内容：
WAIT #1: nam='db file scattered read' ela= 0 p1=1 p2=4986 p3=128

p3就是Oracle一次IO的块数。

来自 “ ITPUB博客 ” ，链接：http://blog.itpub.net/9925929/viewspace-967748/，如需转载，请注明出处，否则将追究法律责任。

转载于:http://blog.itpub.net/9925929/viewspace-967748/