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043-140

原创 Linux操作系统 作者:jbymy2000 时间:2012-03-09 16:09:57 0 删除 编辑
140. You have configured Automatic Shared Memory Management. Which fo
ur memory structures would be automatically tuned? (Choose four)
A. log buffer
B. Java pool
C. Large pool
D. Fixed SGA
E. Shared pool
F. Streams pool
G. Keep buffer cache
H. Database buffer cache
Answer: B, C, E, H
SQL> select instance_name,version from v$instance ;
INSTANCE_NAME VERSION
---------------- -----------------
mydb 10.2.0.1.0
Elapsed: 00:00:00.00
sys@mydb(10.168.0.202) SQL> host ;
[oracle@mailserver ~]$ strings /u01/app/oracle/dbs/spfilemydb.ora | grep __
mydb.__db_cache_size=3120562176
mydb.__java_pool_size=16777216
mydb.__large_pool_size=83886080
mydb.__shared_pool_size=805306368
mydb.__streams_pool_size=33554432
实际上Streams Pool 在Oracle 10g R2 中纳入ASMM(auto segment space management)的
调整范围了,题目问的是4 个参数,估计还是立足于Oracle 10g R1 这个版本咯。
当管理员设置了 SGA_TARGET 的值后,Oracle 10g 会自动地设定各个 SGA 内存组件,包括:
1.共享池(shared pool)(供 SQL and PL/SQL 执行使用)
2.Java 池(Java pool)(供 Java 执行使用)
3.大型池(large pool)(供大块的内存分配使用,例如 RMAN 备份时所需
缓冲区)
4.数据缓存区(buffer cache) 即Database buffer cache
5.数据流池(streams pool)
管理员无需为这些内存组件显式地设置容量。默认情况下这些内存组件的参
数值将显示为零。当某个内存组件需要更多的内存时,可以通过 Oracle 内
部的自动调整机制从其他组件获取。这些工作对用户而言是透明的,无需人
工干预。
Select * from v$sga_dynamic_components
SGA 所有的组件:
• Database buffer cache: Caches blocks of data retrieved from disk
• Redo log buffer: Caches redo information until it can be written to disk
• Shared pool: Caches various constructs that can be shared among users
• Large pool: Optional area used for buffering large I/O requests in support of
parallel query,shared server, Oracle XA, and certain types of backup operations
• Java pool: Holds session-specific Java code and data within the Java Virtual
Machine(JVM)
• Streams pool: Used by Oracle Streams
• Keep buffer cache: Holds data that is kept in the buffer cache as long as possible
• Recycle buffer cache: Holds data that is quickly aged out of the buffer cache
• nK block size buffer caches: Caches data blocks that are of a different size than
the default database block size; used to support transportable tablespaces
注意:log buffer 不能自动管理

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