MMAN - Oracle 10g的Memory manager进程

MMAN进程是Oracle 10g引入用于进行内存管理的进程，在进行动态内存调整时，这个进程要发挥其作用。
在文档上，Oracle说，这个进程的作用是内部数据库任务的执行者：MMAN is used for internal database tasks.

这里的内部任务显然包括自动的内存调整，但是不排除还有其他使命。
当进行内存调整时，有一个等待事件于此有关：

SGA: MMAN sleep for component shrink

MMAN to wait and post itself for satisfying an auto-tuned memory request while trying to fully free a component's quiesced granules. In Release 10.1, the name of this event was 'wait for SGA component shrink'.

在后台转储跟踪，可以看到MMAN进程的等待：

*** 2009-12-22 15:00:04.484
WAIT #0: nam='rdbms ipc message' ela= 2999944 timeout=300 p2=0 p3=0 obj#=-1 tim=9809590317
WAIT #0: nam='rdbms ipc message' ela= 2999773 timeout=300 p2=0 p3=0 obj#=-1 tim=9812737808
WAIT #0: nam='rdbms ipc message' ela= 2999664 timeout=300 p2=0 p3=0 obj#=-1 tim=9815814982
WAIT #0: nam='SGA: MMAN sleep for component shrink' ela= 10045 component id=6 current size=8 target size=7 obj#=-1 tim=9815936073
WAIT #0: nam='SGA: MMAN sleep for component shrink' ela= 10581 component id=6 current size=8 target size=7 obj#=-1 tim=9815946809
WAIT #0: nam='SGA: MMAN sleep for component shrink' ela= 10541 component id=6 current size=8 target size=7 obj#=-1 tim=9815957544
WAIT #0: nam='SGA: MMAN sleep for component shrink' ela= 10655 component id=6 current size=8 target size=7 obj#=-1 tim=9815968290
WAIT #0: nam='SGA: MMAN sleep for component shrink' ela= 10649 component id=6 current size=8 target size=7 obj#=-1 tim=9815979031
WAIT #0: nam='SGA: MMAN sleep for component shrink' ela= 10645 component id=6 current size=8 target size=7 obj#=-1 tim=9815989770
WAIT #0: nam='SGA: MMAN sleep for component shrink' ela= 10678 component id=6 current size=8 target size=7 obj#=-1 tim=9816000516
WAIT #0: nam='SGA: MMAN sleep for component shrink' ela= 10661 component id=6 current size=8 target size=7 obj#=-1 tim=9816011260
WAIT #0: nam='SGA: MMAN sleep for component shrink' ela= 10644 component id=6 current size=8 target size=7 obj#=-1 tim=9816022006
WAIT #0: nam='SGA: MMAN sleep for component shrink' ela= 10623 component id=6 current size=8 target size=7 obj#=-1 tim=9816032746
WAIT #0: nam='SGA: MMAN sleep for component shrink' ela= 10664 component id=6 current size=8 target size=7 obj#=-1 tim=9816043506
WAIT #0: nam='rdbms ipc message' ela= 2449387 timeout=245 p2=0 p3=0 obj#=-1 tim=9818925363

然而在很多繁忙的环境中，自动的内存调整会成为一个负担，所以很多用户禁用了这一功能。


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