419.In Oracle 11g, by default which one of the following conditions implicitly enables Automatic PGA Memory Management?
A. Setting a nonzero value for SGA_TARGET
B. Configuring Automatic Shared Memory Management
C. Configuring Automatic Memory Management
D. Setting a nonzero value for SGA_MAX_SIZE and PGA_AGGREGATE_TARGET
E. None of the above
Answer: B

参考：http://docs.oracle.com/cd/E11882_01/server.112/e10897/instance.htm#ADMQS12038

在Oracle 11g中，默认情况下，以下哪一个条件隐含地启用自动PGA内存管理？

By default, Oracle 11g is configured for Automatic Memory Management. If you configure Automatic Shared Memory Management and make no other changes, you will implicitly enable Automatic PGA Memory Management. Setting SGA_TARGET to a nonzero value doesn‘t immediately enable Automatic Shared Memory Management because you may still have Automatic Memory Management enabled. Setting the parameter SGA_MAX_SIZE to nonzero puts a cap on manual SGA configuration, but again it does not implement Manual Shared Memory Management. The value of PGA_AGGREGATE_TARGET is relevant only if Automatic Memory Management is not configured, so you must also set MEMORY_TARGET to zero for it to take effect.
默认情况下，Oracle 11g的配置为自动内存管理AMM，如果配置了自动共享内存管理ASMM，并没有其他的变化，你将隐式启用自动PGA内存管理。
SGA_TARGET设置为非零值不会立即启用自动共享内存管理，因为您仍然可以启用自动内存管理。SGA_MAX_SIZE设置为非零为手动SGA配置参数设置上限，但它没有实现共享内存手动管理。PGA_AGGREGATE_TARGET的值是相关的，仅当未配置自动内存管理时，所以您还必须设置MEMORY_TARGET为零以生效。