518.The DBA has chosen to manage SGA and PGA memory separately in an OLTP database because of
his unique knowledge of the application. Which of these are good starting points to use when configuring
the maximum values for SGA and PGA, based on the amount of memory available on the system?
A. 20% SGA, 80% PGA
B. 25% SGA, 75% PGA
C. 50% SGA, 50% PGA
D. 75% SGA, 25% PGA
E. 80% SGA, 20% PGA
Answer: E
答案解析：
参考：http://docs.oracle.com/cd/E11882_01/server.112/e41573/memory.htm#PFGRF94352
7.5.1.1 Setting PGA_AGGREGATE_TARGET Initially
The value of the PGA_AGGREGATE_TARGET initialization parameter (for example 100000 KB, 2500 MB, or 50 GB) should be set based on the total amount of memory available for the Oracle database instance. This value can
then be tuned and dynamically modified at the instance level. Example 7-2 illustrates a typical situation.
Example 7-2 Initial Setting of PGA_AGGREGATE_TARGET
Assume that an Oracle database instance is configured to run on a system with 4 GB of physical memory. Part of that memory should be left for the operating system and other non-Oracle applications running on the same hardware system. You might decide to dedicate only 80% (3.2 GB) of the available memory to the Oracle database instance.
You must then divide the resulting memory between the SGA and the PGA.
-
For OLTP systems, the PGA memory typically accounts for a small fraction of the total memory available (for example, 20%), leaving 80% for the SGA.
-
For DSS systems running large, memory-intensive queries, PGA memory can typically use up to 70% of that total (up to 2.2 GB in this example).
Good initial values for the parameter PGA_AGGREGATE_TARGET might be:
-
For OLTP
:PGA_AGGREGATE_TARGET= (total_mem* 80%) * 20% -
For DSS
:PGA_AGGREGATE_TARGET= (total_mem* 80%) * 50%where
total_memis the total amount of physical memory available on the system.
In this example, with a value of total_mem equal to 4 GB, you can initially set PGA_AGGREGATE_TARGET to 1600 MB for a DSS system and to 655 MB for an OLTP system.