ORACLE_修改实例的内存大小

一：修改oracle数据库实例内存大小脚本

  1  ---- 1、操作 （oracle使用内存约等于 SGA+PGA，所以可以减少SGA与PGA解决你的问题，生产库慎用）
  2 alter system set sga_max_size=100m scope=spfile; --减少SGA大小，静态参数，重启后生效
  3 alter system set sga_target=80m scope=both; --动态参数；oracle推荐：启动时修改此参数，不要动态设置此参数
  4 alter system set pga_aggregate_target=40m sope=both; ---减少pga大小

 

二：知识点拓展：

SGA_MAX_SIZE的大小不是随意指定的，必须满足一定条件的。
sga_max_size=100M,必须满足SGA所有组件的最小和；至少满足db_cache_size,log_buffer,shared_pool_size,large_pool_size,java_pool_size总和的大小)

  1 oracle内存结构介绍：
  2 Introduction to Oracle Memory Structures
  3 Oracle uses memory to store information such as the following:
  4 
  5 Program code
  6 Information about a connected session, even if it is not currently active
  7 Information needed during program execution (for example, the current state of a query from which rows are being fetched)
  8 Information that is shared and communicated among Oracle processes (for example, locking information)
  9 Cached data that is also permanently stored on peripheral memory (for example, data blocks and redo log entries)
 10 The basic memory structures associated with Oracle include:
 11 System Global Area (SGA), which is shared by all server and background processes.
 12 Program Global Areas (PGA), which is private to each server and background process; there is one PGA for each process.
 13 
 14 1.sqlplus “/ as sysdba"  2. 3.create pfile='d:/cj.ora' from spfile;  然后去你的oracle安装目录
 15 　　找一个init数据库名。ora这样一个文件
 16 
 17 　　把几个oracle内存参数改小点
 18 
 19 　　一个2G的内存是如下配置的：
 20 
 21 　　*.sga_max_size=712M
 22 
 23 　　*.large_pool_size=8M
 24 
 25 　　*.shared_pool_size=250M
 26 
 27 　　*.sort_area_size=0.5M
 28 
 29 　　*.db_cache_size=350M
 30 
 31 　　然后shutdown数据库
 32 
 33 　　1.shutdown immediate;  2. 3.create spfile from pfile='d:/cj2.ora';  4. 5.startup;  然后启动，就可以了。
 34 
 35 　　以上就是调整oracle内存参数，减少数据库内存占用的方法介绍。
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