运行在操作系统上的进程存在2种系统时序优先级模式:即 实时模式 Real Time(RT) mode, 与分时模式 Time Sharing(TS) mode. 绝大多数Oracle进程运行在TS模式下：
如上所示所有进程均运行在TS模式下且priority均为23|24. Oracle一般不推荐使用RT模式，因为虽然个别进程可以通过这种方式获得更多的CPU资源，但往往系统的瓶颈并非CPU,即尽管CPU使用率高了，但实际系统TPS并未得到提升。 在10gr2版本后RAC中的LMS进程成为唯一一个使用RT模式的Oracle进程，我们可以通过查询参数_high_priority_processes了解相关信息：
_high_priority_processes通过进程功能名进行匹配，下面我们将提高LGWR及PMON进程的优先级：
好了lgwr和pmon进程也进入实时模式了，同时priority值上升到了41. 注意： Oracle默认仅允许LMS进程（11g中多了VKTM进程）使用RT模式是有它的原因的，所以如果不是Oracle support 推荐，您没有任何修改隐式参数的理由。 其次根据Oracle文档[ID 602419.1]的描述，oradism文件(该文件位于$ORACLE_HOME/bin目录下）不正确的权限将导致RT模式无法被正确使用，该文件默认属于root用户并具有s权限。如下测试：
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[oracle@rh1 ~]$ ps -efc|grep ora_|grep -v grep
oracle 8510 1 TS 23 Mar27 ? 00:00:02 ora_pmon_PROD
oracle 8512 1 TS 23 Mar27 ? 00:00:00 ora_psp0_PROD
oracle 8514 1 TS 23 Mar27 ? 00:00:00 ora_mman_PROD
oracle 8516 1 TS 23 Mar27 ? 00:00:02 ora_dbw0_PROD
oracle 8518 1 TS 23 Mar27 ? 00:00:04 ora_lgwr_PROD
oracle 8520 1 TS 23 Mar27 ? 00:00:04 ora_ckpt_PROD
oracle 8522 1 TS 23 Mar27 ? 00:00:08 ora_smon_PROD
oracle 8524 1 TS 23 Mar27 ? 00:00:00 ora_reco_PROD
oracle 8526 1 TS 23 Mar27 ? 00:00:34 ora_cjq0_PROD
oracle 8528 1 TS 23 Mar27 ? 00:00:06 ora_mmon_PROD
oracle 8530 1 TS 24 Mar27 ? 00:00:07 ora_mmnl_PROD
oracle 8538 1 TS 23 Mar27 ? 00:00:00 ora_arc0_PROD
oracle 8540 1 TS 23 Mar27 ? 00:00:00 ora_arc1_PROD
oracle 8548 1 TS 23 Mar27 ? 00:00:00 ora_qmnc_PROD
oracle 8555 1 TS 23 Mar27 ? 00:00:00 ora_q000_PROD
oracle 8559 1 TS 23 Mar27 ? 00:00:00 ora_q001_PROD
oracle 30500 1 TS 23 22:10 ? 00:00:00 ora_j000_PROD
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SQL> col
name
format a40
SQL>
SELECT
x.ksppinm
NAME
, y.ksppstvl VALUE
2
FROM
SYS.x$ksppi x, SYS.x$ksppcv y
3
WHERE
x.inst_id = USERENV (
'Instance'
)
4
AND
y.inst_id = USERENV (
'Instance'
)
5
AND
x.indx = y.indx
6
AND
x.ksppinm
LIKE
'%priority%'
;
NAME
VALUE
---------------------------------------- ----------
_high_priority_processes LMS*
_os_sched_high_priority 1
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SQL>
alter
system
set
"_high_priority_processes"
=
'LMS*|LGWR|PMON'
scope=spfile;
System altered.
SQL> startup
force
;
ORACLE instance started.
Total System
Global
Area 281018368 bytes
Fixed
Size
2083336 bytes
Variable
Size
150996472 bytes
Database
Buffers 121634816 bytes
Redo Buffers 6303744 bytes
Database
mounted.
Database
opened.
SQL> !ps -efc|grep ora_|grep -v grep
oracle 31441 1 RR 41 22:50 ? 00:00:00 ora_pmon_PROD
oracle 31445 1 TS 23 22:50 ? 00:00:00 ora_psp0_PROD
oracle 31447 1 TS 23 22:50 ? 00:00:00 ora_mman_PROD
oracle 31449 1 TS 23 22:50 ? 00:00:00 ora_dbw0_PROD
oracle 31451 1 RR 41 22:50 ? 00:00:00 ora_lgwr_PROD
oracle 31455 1 TS 23 22:50 ? 00:00:00 ora_ckpt_PROD
oracle 31457 1 TS 23 22:50 ? 00:00:00 ora_smon_PROD
oracle 31459 1 TS 22 22:50 ? 00:00:00 ora_reco_PROD
oracle 31461 1 TS 23 22:50 ? 00:00:01 ora_cjq0_PROD
oracle 31463 1 TS 23 22:50 ? 00:00:01 ora_mmon_PROD
oracle 31465 1 TS 24 22:50 ? 00:00:00 ora_mmnl_PROD
oracle 31471 1 TS 24 22:50 ? 00:00:00 ora_p000_PROD
oracle 31473 1 TS 24 22:50 ? 00:00:00 ora_p001_PROD
oracle 31475 1 TS 24 22:50 ? 00:00:00 ora_arc0_PROD
oracle 31477 1 TS 22 22:50 ? 00:00:00 ora_arc1_PROD
oracle 31481 1 TS 23 22:50 ? 00:00:00 ora_qmnc_PROD
oracle 31488 1 TS 23 22:50 ? 00:00:00 ora_q000_PROD
oracle 31490 1 TS 23 22:50 ? 00:00:00 ora_q001_PROD
oracle 31500 1 TS 23 22:50 ? 00:00:00 ora_j000_PROD
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[oracle@rh1 bin]$ ls -la oradism
-r-sr-s--- 1 root oinstall 14931 Mar 11 2008 oradism
[oracle@rh1 bin]$ su - root
Password:
[root@rh1 ~]# chown oracle:oinstall /s01/oracle/product/10.2.0/db_1/bin/oradism
[root@rh1 ~]#
exit
logout
[oracle@rh1 bin]$ ls -la oradism
-r-xr-x--- 1 oracle oinstall 14931 Mar 11 2008 oradism
[oracle@rh1 bin]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.4.0 - Production on Sun Mar 28 23:07:03 2010
Copyright (c) 1982, 2007, Oracle. All Rights Reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL>
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup;
ORACLE instance started.
Total System Global Area 281018368 bytes
Fixed Size 2083336 bytes
Variable Size 150996472 bytes
Database Buffers 121634816 bytes
Redo Buffers 6303744 bytes
Database mounted.
Database opened.
SQL> col name format a35;
SQL> col value format a10;
SQL> SELECT x.ksppinm NAME, y.ksppstvl VALUE
2 FROM SYS.x$ksppi x, SYS.x$ksppcv y
3 WHERE x.inst_id = USERENV (
'Instance'
)
4 AND y.inst_id = USERENV (
'Instance'
)
5 AND x.indx = y.indx
6 AND x.ksppinm LIKE
'%priority%'
;
NAME VALUE
----------------------------------- ----------
_high_priority_processes LMS*|LGWR|PMON
_os_sched_high_priority 1
SQL> !ps -efc|grep ora_|grep -v grep
oracle 31994 1 TS 23 23:07 ? 00:00:00 ora_pmon_PROD
oracle 31998 1 TS 23 23:07 ? 00:00:00 ora_psp0_PROD
oracle 32000 1 TS 23 23:07 ? 00:00:00 ora_mman_PROD
oracle 32002 1 TS 23 23:07 ? 00:00:00 ora_dbw0_PROD
oracle 32004 1 TS 24 23:07 ? 00:00:00 ora_lgwr_PROD
oracle 32008 1 TS 22 23:07 ? 00:00:00 ora_ckpt_PROD
oracle 32010 1 TS 23 23:07 ? 00:00:00 ora_smon_PROD
oracle 32012 1 TS 22 23:07 ? 00:00:00 ora_reco_PROD
oracle 32014 1 TS 23 23:07 ? 00:00:01 ora_cjq0_PROD
oracle 32016 1 TS 23 23:07 ? 00:00:01 ora_mmon_PROD
oracle 32018 1 TS 24 23:07 ? 00:00:00 ora_mmnl_PROD
oracle 32026 1 TS 24 23:07 ? 00:00:00 ora_arc0_PROD
oracle 32028 1 TS 23 23:07 ? 00:00:00 ora_arc1_PROD
oracle 32032 1 TS 23 23:07 ? 00:00:00 ora_qmnc_PROD
oracle 32045 1 TS 23 23:07 ? 00:00:00 ora_q000_PROD
oracle 32065 1 TS 23 23:08 ? 00:00:00 ora_q001_PROD
oracle 32072 1 TS 23 23:08 ? 00:00:00 ora_j000_PROD
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that's great, 显然oradism不仅为Oracle实例提供了内存资源控制功能，还包括了进程优先级分配的权限。 我们应当再次声明hidden parameter不应“滥用”于production environment.
本文转自maclean_007 51CTO博客，原文链接:http://blog.51cto.com/maclean/1277075
