oracle11g 自动内存管理

11g开始，能自动管理sga,pga，称为amm
MEMORY_MAX_TARGE：这个参数指定了 MEMORY_TARGET这个参数能够设置的最大值，memory_target这个参数指定了系统级别的可用内存，可以根据需要减少或增加sga,pga的大小。在一个基于文本的参数文件中，如果排除掉 MEMORY_MAX_TARGET 参数并包含MEMORY_TARGET这个参数，那么数据库会动态的设置memory_max_target为memory_target，如果排除掉MEMORY_TARGET 这个参数，并包含MEMORY_MAX_TARGET这个参数，memory_target参数默认为0，启动后，你可以设置memory_target为非0，并不超过MEMORY_MAX_TARGET的大小。
监控amm
select * from vmemorytargetadviceorderbymemorysize大多数的情况下，我们是使用手工分配内存的。对于pga，设置了target大小，也是自动管理的。对于asmm,sgatarget参数指定了sga可用的大小。granulesThememoryfordynamiccomponentsintheSGAisallocatedintheunitofgranules.GranulesizeisdeterminedbytotalSGAsize.Generallyspeaking,onmostplatforms,ifthetotalSGAsizeisequaltoorlessthan1GB,thengranulesizeis4MB.ForSGAslargerthan1GB,granulesizeis16MB.Someplatformdependenciesmayarise.Forexample,on32−bitWindowsNT,thegranulesizeis8MBforSGAslargerthan1GB.Consultyouroperatingsystemspecificdocumentationformoredetails.select∗fromvsgainfo;
select * from vsgatargetadviceorderbysgasize;设置sgaSELECT((SELECTSUM(value)FROMVSGA) -
(SELECT CURRENT_SIZE FROM V$SGA_DYNAMIC_FREE_MEMORY)
) “SGA_TARGET”
FROM DUAL;

启用自动sga管理，但是有些部件是不能自动管理的，包括三部分：
nk buffer(非默认块的buffer)；log buffer；keep&recycle buffer；
这些非自动管理组件必须手工设定，自动分配的内存是sga_target减去这部分大小。

amm情况下转换成asmm
1ALTER SYSTEM SET MEMORY_TARGET = 0;
2将sga各个内存池设置成0
SGA_TARGET 这个参数可以动态调整变大或变小。
为了使用手工管理共享内存，
1设置MEMORY_TARGET =0
2设置SGA_TARGET =0，并设置sga各个组件的大小。
在设置了sga_target后，依然可以设置sga各个组件的大小，保证各个组件的在动态调整的时候不低于设置的值。
如果设置了PGA_AGGREGATE_TARGET，oracle会确保所有的server process和后台进程的内存分配不会超过这个值。

自动pga管理下的监控视图

V$SYSSTAT

V$SESSTAT

V$PGASTAT

V$SQL_WORKAREA

V$SQL_WORKAREA_ACTIVE

v$process中的

PGA_USED_MEM

PGA_ALLOCATED_MEM

PGA_MAX_MEM

三列

手工 管理pga的设置

SORT_AREA_SIZE, HASH_AREA_SIZE, BITMAP_MERGE_AREA_SIZE and CREATE_BITMAP_AREA_SIZE

If you decide to tune SQL work areas manually, you must set the WORKAREA_SIZE_POLICY initialization parameter to MANUAL.

内存管理视图

View    DescriptionV$SGA  Displays summary information about the system global area (SGA).V$SGAINFO  Displays size information about the SGA, including the sizes of different SGA components, the granule size, and free memory.V$SGASTAT  Displays detailed information about how memory is allocated within the shared pool, large pool, Java pool, and Streams pool.V$PGASTATDisplays PGA memory usage statistics as well as statistics about the automatic PGA memory manager when it is enabled (that is, when PGA_AGGREGATE_TARGET is set). Cumulative values in V$PGASTAT are accumulated since instance startup.V$MEMORY_DYNAMIC_COMPONENTS    Displays information on the current size of all automatically tuned and static memory components, with the last operation (for example, grow or shrink) that occurred on each.V$SGA_DYNAMIC_COMPONENTS   Displays the current sizes of all SGA components, and the last operation for each component.V$SGA_DYNAMIC_FREE_MEMORY  Displays information about the amount of SGA memory available for future dynamic SGA resize operations.V$MEMORY_CURRENT_RESIZE_OPS    Displays information about resize operations that are currently in progress. A resize operation is an enlargement or reduction of the SGA, the instance PGA, or a dynamic SGA component.V$SGA_CURRENT_RESIZE_OPS   Displays information about dynamic SGA component resize operations that are currently in progress.V$MEMORY_RESIZE_OPS    Displays information about the last 800 completed memory component resize operations, including automatic grow and shrink operations for SGA_TARGET and PGA_AGGREGATE_TARGET.V$SGA_RESIZE_OPS   Displays information about the last 800 completed SGA component resize operations.V$MEMORY_TARGET_ADVICE Displays information that helps you tune MEMORY_TARGET if you enabled automatic memory management.V$SGA_TARGET_ADVICE    Displays information that helps you tune SGA_TARGET.V$PGA_TARGET_ADVICE    Displays information that helps you tune PGA_AGGREGATE_TARGET.

在测试环境中，关闭amm，开启asmm,自动pga管理重启oracle后，发现memory_max_target参数依然会有值，参考http://blog.csdn.net/ghostliming/article/details/49081559
使用参数文件，在参数文件中去掉该值，此时参数文件中，这个值其实已经为0了，在启动，查看参数已被置为0。