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正确答案：CD（题库给出的答案是AD，大家要相信自己，有些答案是错的！一切以实战为依据）

一、我们先来看Oracle 11g内存架构图，来自OCP教材：

二、内存参数的一些关系：

memory_max_target、 memory_target、sga_max_size、sga_target、pga_aggregate_target

  １、   sga_target＝0 ，pga_aggregate_target＝0 －〉完全自动管理，SGA＝memory_target*60%   PGA＝memory_target*40%

  ２、   sga_target＝600（最小值） ，pga_aggregate_target＝200（最小值） －〉memory_target＝sga_target+pga_aggregate_target

   ３、  sga_target＝600，pga_aggregate_target＝0  －〉pga_aggregate_target＝memory_target－sga_target

   ４、  sga_target＝0，pga_aggregate_target＝200  －〉sga_target＝memory_target－pga_aggregate_target

了解了内存的基本知识后，我们一起来解题：

答案A，不正确

根据题意，我们来实验一把：

１、设置参数

sys@OCM> alter system set memory_max_target=0 scope=spfile;

System altered.

sys@OCM> alter system set memory_target=804M;

System altered.

sys@OCM> alter system set pga_aggregate_target=90M;

System altered.

sys@OCM> alter system set sga_target=270M;

System altered.

２、重启数据库，报错如下

sys@OCM> startup force;
ORA-00837: Specified value of MEMORY_TARGET greater than MEMORY_MAX_TARGET
sys@OCM> show parameter mem
ORA-01034: ORACLE not available
Process ID: 0
Session ID: 148 Serial number: 493

３、  从spfile创建出一个pfile

sys@OCM> create pfile='/tmp/pfile.ora' from spfile;
ERROR:
OCI-21710: argument is expecting a valid memory address of an object



File created.

４、  查pfile中memory_max_target的值，结果看到：

[root@mydb tmp]# more　/temp/pfile.ora
ocm.__db_cache_size=343932928
ocm.__java_pool_size=4194304
ocm.__large_pool_size=4194304
ocm.__oracle_base='/u01/app/oracle'#ORACLE_BASE set from environment
ocm.__pga_aggregate_target=159383552
ocm.__sga_target=683671552
ocm.__shared_io_pool_size=0
ocm.__shared_pool_size=314572800
ocm.__streams_pool_size=4194304
*.audit_file_dest='/u01/app/oracle/admin/ocm/adump'
*.audit_trail='db'
*.compatible='11.2.0.0.0'
*.control_files='/u01/app/oracle/oradata/ocm/control01.ctl','/u01/app/oracle/oradata/ocm/control02.ctl'
*.db_block_size=8192
*.db_domain=''
*.db_name='ocm'
*.diagnostic_dest='/u01/app/oracle'
*.dispatchers='(PROTOCOL=TCP) (SERVICE=ocmXDB)'
*.log_archive_dest_1='location=/arch'
*.memory_max_target=0
*.memory_target=842006528
*.open_cursors=300
*.pga_aggregate_target=94371840
*.processes=150
*.remote_login_passwordfile='EXCLUSIVE'
*.sga_target=285212672
*.undo_tablespace='UNDOTBS1'

　　从上面的参数可以看出memory_max_target=0，还没有自动变为804M,所以不正确。实际上memory_max_target是控制memory_target的值不能超过它。

答案B，不正确，我们从上面的参数可以看出：pga_aggregate_target=94371840和sga_target=285212672，而并非为0