OCP-V13-701

A. Because the PGA_AGGREGATE_TARGET parameter is not set

B. Because the STATISTICS_LEVEL parameter is set to BASIC

C. Because MEMORY_TARGET and MEMORY_MAX_TARGET cannot be equal

D. Because both the SGA_TARGET and MEMORY_TARGET parameters are set.

Correct Answer: B

Section: (none)

Explanation

Explanation/Reference:

应该是B。

关键在于 STATISTICS_LEVEL 被设置成了basic

Setting SGA Target Size

You enable the automatic shared memory management feature by setting the SGA_TARGET parameter to

a nonzero value. This parameter in effect replaces the parameters that control the memory allocated for a

specific set of individual components, which are now automatically and dynamically resized (tuned) as

needed.

Note:The STATISTICS_LEVEL initialization parameter must be set to TYPICAL (the

default) or ALL for automatic shared memory management to function.

D) check sga_target and memory target set together

SQL> show parameter memory

NAME TYPE VALUE

hi_shared_memory_address integer 0

memory_max_target big integer 1408M

memory_target big integer 1408M

shared_memory_address integer 0

SQL> show parameter sga

NAME TYPE VALUE

lock_sga boolean FALSE

pre_page_sga boolean FALSE

sga_max_size big integer 1408M

sga_target big integer 1008M

SQL>

statistics_level 参数是oracle9.2开始引入的一个控制系统统计参数收集的一个开关.一共有三个值:basic,typical,all.支持alter session,alter system 动态修改.如果要用statspack或者AWR收集系统性能统计数据.那么这个参数的值必须为typical或all.通常all是一个全面收集,包括 OS以及sql执行路径方面的一些统计信息,除非遇见非常严重的性能问题或在一些特殊的性能挣断方面才会用到statistics_level=all, 平常statistics_level=typeical已经足够诊断99%的性能问题了. 
example: seting statistics_level 

alter system set statistics_level=basic; 
alter system set statistics_level=typical; 
alter system set statistics_level=all; 
or 
alter session set statistics_level=basic; 
alter session set statistics_level=typical; 
alter session set statistics_level=all; 

statistics_level=basic的情况下,oracle关闭了所有性能数据的收集,也就是如果要关闭AWR或statspack收集,只要设置alter system set statistics_level=basic;就行了; 

statistics_level=typical的时 
候,除了plan_executetion_statistics和OS Statistics不能收集外,其他的都可以收集,如要要收集这个两项,必须设置statistics_level=all; 

如果当statistics_level=ALL,系统收集所有的统计信息.

设置 STATISTICS_LEVEL = BASIC 会禁用一下oracle 的功能特性

Automatic Workload Repository (AWR) Snapshots

Automatic Database Diagnostic Monitor (ADDM)

All server-generated alerts

Automatic SGA Memory Management （ASMM）和自动内存管理

Automatic optimizer statistics collection

Object level statistics

End to End Application Tracing (V$CLIENT_STATS)

Database time distribution statistics (V$SESS_TIME_MODEL and V$SYS_TIME_MODEL)

Service level statistics

Buffer cache advisory

MTTR advisory

Shared pool sizing advisory

Segment level statistics

PGA Target advisory

Timed statistics

Monitoring of statistics