前接天需要改一下Oracle的内存参数，本来oracle 装机时候已经配置好了sga 和pga的大小了，但是有好多问题随之出现。linux 用的是16G内存，sga 内存12G，pga 4G,所以linux 系统很慢。
改打开连接数：
SQL>show parameter open_cursors; ---显示参数值
SQL>alter system set open_cursors = 1000; ---修改参数值为1000
SQL>commit; ----提交
修改成功。
（转）Oracle 调整SGA、PGA大小
博客分类： Oracle
SQL> show parameter sga;
SQL> alter system set sga_max_size=4096M scope=spfile;
System altered.
SQL> alter system set sga_target=4096M scope=spfile;
System altered.
如果是RAC环境，需要这样增加sid='*'：
alter system set sga_target=20G scope=spfile sid='*';
重启使更改生效：
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 4294967296 bytes
Fixed Size 2026296 bytes
Variable Size 805307592 bytes
Database Buffers 3472883712 bytes
Redo Buffers 14749696 bytes
Database mounted.
Database opened.
SQL> show parameter sga;
NAME TYPE VALUE
----------- ------------------------------
lock_sga boolean FALSE
pre_page_sga boolean FALSE
sga_max_size big integer 4G
sga_target big integer 4G
SQL> show parameter pga；
不用重启DB，直接在线修改。
SQL> alter system set workarea_size_policy=auto scope=both;
System altered.
SQL> alter system set pga_aggregate_target=512m scope=both;
System altered.
SQL> show parameter workarea
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
workarea_size_policy string AUTO --这个设置成AUTO
SQL> show parameter pga
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
pga_aggregate_target big integer 536870912
SELECT * FROM V$PGASTAT;
aggregate PGA auto target 477379584 bytes --当前可用于自动分配了的PGA大小，应该比PGA_AGGREGATE_TARGET 小
over allocation count 1118 --实例启动后，发生的分配次数，如果这个值大于0，就要考虑增加pga的值
1 查看 SGA大小 show parameter sga_max_size db_cache_size的尺寸受 SGA的影响为能大于SGA
2 查看 show parameter shared_pool_size 尺寸
一般来说 shared_pool_size+db_cache_size=SGA_MAX_SIZE*70%左右
经过计算再修改db_cache_size
sql>alter system set db_cache_size= 大小M scope=spfile sid='数据库SID';
sql>shutdown immediate
sql>startup
sql>show parameter db_cache_size
就可以看到修改后的效果了
[oracle@oracle_db ~]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.4.0 - Production on Wed Aug 5 21:56:47 2015
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>
SQL>
SQL> show parameter sga;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
lock_sga boolean FALSE
pre_page_sga boolean FALSE
sga_max_size big integer 12G
sga_target big integer 12G
SQL> alter system set sga_max_size=10240M scope=spfile;
System altered.
SQL> alter system set sga_target=10240M scope=spfile;
System altered.
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 1.0737E+10 bytes
Fixed Size 2101808 bytes
Variable Size 1560284624 bytes
Database Buffers 9160359936 bytes
Redo Buffers 14671872 bytes
Database mounted.
Database opened.
SQL> show parameter sga;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
lock_sga boolean FALSE
pre_page_sga boolean FALSE
sga_max_size big integer 10G
sga_target big integer 10G
SQL> show parameter pga；
SQL> alter system set workarea_size_policy=auto scope=both;
System altered.
SQL> alter system set pga_aggregate_target=2048m scope=both;
System altered.
SQL> show parameter workarea
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
workarea_size_policy string AUTO
SQL> show parameter workarea
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
workarea_size_policy string AUTO
SQL> show parameter pga；
SQL> show parameter sga;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
lock_sga boolean FALSE
pre_page_sga boolean FALSE
sga_max_size big integer 10G
sga_target big integer 10G
SQL>
SQL>
SQL> SQL>
最后的结果是改成sga 10G + pga 2G ,系统内存 4G，swap 分区 内存32G。
改后效果并不是很明显，需要后续观察
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