memory_max_target memory_target on oracle 11g

Oracle9i引入pga_aggregate_target，可以自动对PGA进行调整；
Oracle10引入sga_target，可以自动对SGA进行调整。
Oracle11g则对这两部分进行综合，引入memory_target，可以自动调整所有的内存，这就是新引入的自动内存管理特性。
设置memory_target参数后，实际上Oracle会自动设置并调整以下两个参数来分配SGA和PGA的内存，这和Oracle10g自动设置sga_target后分配db_cache_size和shared_pool_size的机制是一样的

[code]SQL> show parameter memory

hi_shared_memory_address integer 0
memory_max_target big integer 128M
memory_target big integer 128M
shared_memory_address integer 0
SQL> alter system set memory_target = 400m scope=both;
alter system set memory_target = 400m scope=both
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-00837: Specified value of MEMORY_TARGET greater than MEMORY_MAX_TARGET

SQL> alter system set memory_max_target = 400m scope=spfile;
SQL> startup force
ORACLE instance started.

Total System Global Area 418484224 bytes
Fixed Size 1336932 bytes
Variable Size 406849948 bytes
Database Buffers 4194304 bytes
Redo Buffers 6103040 bytes
Database mounted.
Database opened.
SQL> show parameter memory

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
hi_shared_memory_address integer 0
memory_max_target big integer 400M
memory_target big integer 128M
shared_memory_address integer 0
SQL> alter system set memory_target = 400m scope=both;
System altered.

SQL> show parameter memory

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
hi_shared_memory_address integer 0
memory_max_target big integer 400M
memory_target big integer 400M
shared_memory_address integer 0
SQL>[/code]