11g中_serial_direct_read是动态参数，可以在线修改

[oracle@rhel63single ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Sun Apr 26 13:54:56 2015

Copyright (c) 1982, 2013, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> alter system set "_serial_direct_read" = false sid = "*";

System altered.

SQL> show parameter serial

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
_serial_direct_read                  string      FALSE
serial_reuse                         string      disable
SQL> show parameter pfile

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
spfile                               string      /u02/app/oracle/product/11.2.0
                                                 .4/db_1/dbs/spfiletest.ora
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.

Total System Global Area 1068937216 bytes
Fixed Size                  2260088 bytes
Variable Size             612369288 bytes
Database Buffers          448790528 bytes
Redo Buffers                5517312 bytes
Database mounted.
Database opened.
SQL> show parameter serial

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
_serial_direct_read                  string      FALSE
serial_reuse                         string      disable
SQL> select x.ksppinm, y.ksppstvl
  2  from x$ksppi x , x$ksppcv y
  3  where x.indx = y.indx
  4  and x.ksppinm like "_serial_direct_read"
  5  order by x.ksppinm; 

KSPPINM
--------------------------------------------------------------------------------
KSPPSTVL
--------------------------------------------------------------------------------
_serial_direct_read
FALSE
[oracle@rhel63single ~]$ sqlplus / as sysdba

SQL*