Oracle OCP 1Z0 053 Q283(Automatic Memory Management)

283.You set the following parameters in the parameter file and restarted the database:
MEMORY_MAX_TARGET=0
MEMORY_TARGET=500M PGA_AGGREGATE_TARGET=90M SGA_TARGET=270M
Which two statements are true regarding these parameters after the database instance is restarted?
(Choose two.)
A. The MEMORY_MAX_TARGET parameter is automatically set to 500 MB.
B. The value of the MEMORY_MAX_TARGET parameter remains zero till it is changed manually.
C. The PGA_AGGREGATE_TARGET and SGA_TARGET parameters are automatically set to zero.
D. The lower bounds of PGA_AGGREGATE_TARGET and SGA_TARGET parameters are set to 90 MB
and 270 MB, respectively.
Answer: AD


當設定了MEMORY_TARGET=500M, 那麼MEMORY_MAX_TARGET自動被設定成500M
當啟用了自動記憶體管理之後，再去設定 PGA_AGGREGATE_TARGET與SGA_TARGET， 這時候SGA_TARGET與PGA_AGGREGATE_TARGET的值就成了下限了。

官方文件：https://docs.oracle.com/cd/B28359_01/server.111/b28310/memory003.htm

In a text initialization parameter file, if you omit the line for MEMORY_MAX_TARGET and include a value for MEMORY_TARGET, the database automatically sets MEMORY_MAX_TARGETto the value of MEMORY_TARGET. If you omit the line for MEMORY_TARGET and include a value for MEMORY_MAX_TARGET, the MEMORY_TARGET parameter defaults to zero. After startup, you can then dynamically change MEMORY_TARGET to a nonzero value, provided that it does not exceed the value of MEMORY_MAX_TARGET.

The preceding steps instruct you to set SGA_TARGET and PGA_AGGREGATE_TARGET to zero so that the sizes of the SGA and instance PGA are tuned up and down as required, without restrictions. You can omit the statements that set these parameter values to zero and leave either or both of the values as positive numbers. In this case, the values act as minimum values for the sizes of the SGA or instance PGA.

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