OCP-1Z0-052-V8.02-64题

64. Which two statements are true about setting the FAST_START_MTTR_TARGET initialization

parameter to a nonzero value? (Choose two.)

A.The MTTR advisor will be disabled.

B.Automatic checkpoint tuning will be enabled. 

C.The value for the LOG_CHECKPOINT_INTERVAL initialization parameter will be override the value for

FAST_START_MTTR_TARGET.

D.The time taken to recover the instance after the crash is always exactly the same as the value given for

the FAST_START_MTTR_TARGET initialization parameter.

Answer: BC  

答案解析：

参考：http://blog.csdn.net/rlhua/article/details/12616383

A。 MTTR advisor禁用，错误。

To enable MTTR Advisor, set the two initialization parameters STATISTICS_LEVEL and FAST_START_MTTR_TARGET.

STATISTICS_LEVEL governs whether all advisors are enabled and is not specific to MTTR Advisor. Ensure that it is set to TYPICAL or ALL. Then, whenFAST_START_MTTR_TARGET is set to a nonzero value, the MTTR Advisor is enabled.

故A错误。

MTTR 指导可将FAST_START_MTTR_TARGET值转换为多个参数，以便在所需时间内（或者在尽量接近此时间的范围内）启用实例恢复。请注意，将禁用

FAST_START_MTTR_TARGET参数显式设置为0会禁用MTTR 指导。

故D错误。是在所需时间内或在尽量接近此事件的范围内，并不是指定的时间点。

FAST_START_MTTR_TARGET参数的设置值必须支持系统的服务级协议。如果MTTR 目标的值较小，则会因增加了数据文件写入次数而增加I/O 开销（这会影响性能）。但是，如果MTTR 目标设置得过大，则实例在崩溃后需要花费较长的时间才会恢复。

而快速启动检查点功能是通过指定所需的非零恢复平均时间（MTTR）值来启用的，该值将用于设置FAST_START_MTTR_TARGET初始化参数。此参数控制数据库对单个实例执行崩溃恢复所花费的时间量。启用快速启动检查点功能时，oracle将自动保持检查点的速度，已便达到请求的MTTR.如果将该值设置为0，将禁用此功能。

故B正确。

  FAST_START_MTTR_TARGET  enables you to specify the number of seconds the database takes to perform crash recovery of a single instance. When specified, FAST_START_MTTR_TARGET  is overridden by  LOG_CHECKPOINT_INTERVAL .

FAST_START_MTTR_TARGET 会被 LOG_CHECKPOINT_INTERVAL所覆盖，故C正确。

官方参考：http://docs.oracle.com/cd/E11882_01/server.112/e40402/initparams090.htm#sthref268

 

Automatic Checkpoint Tuning in 10g [ID 265831.1]

How to enable:

Automatic checkpoint tuning is enabled by default. If it is disabled, by setting the

parameter to zero explicitly, you can enable it by unsetting FAST_START_MTTR_TARGET or

set it to a nonzero value.  If you set this parameter to zero this feature will be disabled.

Note: this is different from defaulting (i.e. not setting) fast_start_mttr_target to 0