639.You want to enable automatic PGA memory management in your database. Which setting is required
to achieve this?
A. Set MEMORY_TARGET to zero
B. Set the STATISTICS_LEVEL parameter to BASIC
C. Set the WORKAREA_SIZE_POLICY parameter to MANUAL
D. Set the PGA_AGGREGATE_TARGET parameter to nonzero value
Answer: D
答案解析：
参考：http://docs.oracle.com/cd/E11882_01/server.112/e25494/memory.htm#ADMIN11233
Using Automatic PGA Memory Management
By default, Oracle Database automatically and globally manages the total amount of memory dedicated to the instance PGA. You can control this amount by setting the initialization parameter PGA_AGGREGATE_TARGET. Oracle
Database then tries to ensure that the total amount of PGA memory allocated across all database server processes and background processes never exceeds this target.
If you create your database with DBCA, you can specify a value for the total instance PGA. DBCA then sets the PGA_AGGREGATE_TARGET initialization parameters in the server parameter file (SPFILE) that
it creates. If you do not specify the total instance PGA, DBCA chooses a reasonable default.
If you create the database with the CREATE DATABASE SQL statement and a text initialization parameter file, you can provide a value for PGA_AGGREGATE_TARGET. If you omit this parameter, the database chooses
a default value.
With automatic PGA memory management, sizing of SQL work areas for all dedicated server sessions is automatic and all *_AREA_SIZE initialization parameters are ignored for these sessions. At
any given time, the total amount of PGA memory available to active work areas on the instance is automatically derived from the parameter PGA_AGGREGATE_TARGET. This amount is set to the value of PGA_AGGREGATE_TARGET minus
the PGA memory allocated for other purposes (for example, session memory). The resulting PGA memory is then allotted to individual active work areas based on their specific memory requirements.
There are dynamic performance views that provide PGA memory use statistics. Most of these statistics are enabled when PGA_AGGREGATE_TARGET is set.