132 Examine the parameter setting in your database: SQL> SHOW PARAMETER TARGET NAME TYPE VALUE -----

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本文讨论了Oracle数据库中自动内存管理的设置与调整方法。通过分析参数设置，确认自动内存管理已启用，并默认按策略分配SGA与PGA内存。此外，还提供了关于如何为新的实例配置合适的PGA_AGGREGATE_TARGET值的指导。

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132
Examine the parameter setting in your database: SQL>
SHOW PARAMETER TARGET
NAME TYPE VALUE
----------------------------- -------------- ----------
archive_lag_target integer 0
db_flashback_retention_target integer 1440
fast_start_io_target integer 0
fast_start_mttr_target integer 0
memory_max_target big integer 808M
memory_target big integer 808M
pga_aggregate_target big integer 0
sga_target big integer 0
SQL> SHOW PARAMETE SGA_MAX_SIZE
NAME TYPE VALUE
------------ ---- ----------
sga_max_size big integer 808M

Which statement is correct about the database?

A. Automatic memory management is disabled because PGA_AGGREGATE_TARGET and
SGA_TARGET are not set
B. The instance is started but the database will not be opened until PGA_AGGREGATE_TARGET and
SGA_TARGET are set
C. The database is opened but users cannot perform transactions until PGA_AGGREGATE_TARGET
and SGA_TARGET are set
D. Automatic memory management is enabled and, as per policy, 60% of the memory for System Global
Area (SGA) and 40% of the memory for Program Global Area (PGA) will be distributed at startup

Correct Answer: D
Section: (none)
Explanation
Explanation/Reference:
Explanation:
Not sure about the policy stuff, but it’s the default behavior when memory_target and memory_max_target
are set, sga_max_target is always set automatically to the same value as memory_max_target
http://download.oracle.com/docs/cd/B14117_01/server.101/b10752/memory.htm#47750

Configuring Automatic PGA Memory
When configuring a brand new instance, it is hard to know precisely the appropriate setting for
PGA_AGGREGATE_TARGET. You can determine this setting in three stages:
Make a first estimate for PGA_AGGREGATE_TARGET, based on a rule of thumb. By default, Oracle
uses
20% of the SGA size. However, this initial setting may be too low for a large DSS system.
Run a representative workload on the instance and monitor performance, using PGA statistics collected
by Oracle, to see whether the maximum PGA size is under-configured or over-configured.
Tune PGA_AGGREGATE_TARGET, using Oracle PGA advice statistics.