Which two statements are true about the interpretation of Buffer Cache Hit Ratio in the
Instance Efficiency Percentages section of an AWR report?(Choose two.)
A.
A high value indicates that the buffer cache is adequately sized for the current workload.
B.
Poor hit ratios indicate that a large number of indexed lookups or small table scans
arebeing performed.
C.
A low hit ratio does not necessarily imply that increasing the size of the buffer cache will
improve performance.
D.
A high hit ratio may indicate that repeated scanning of the same large table or index is
being performed.
E.
A low hit ratio indicates that aKEEPbuffer pool should be configured based on the size of
the largest object accessed in the buffer cache.
agree with C, disagree with E.
D is right.
https://docs.oracle.com/database/121/TGDBA/tune_buffer_cache.htm#TGDBA536
Repeated scanning of the same large table or index can artificially inflate a low cache hit ratio. Examine frequently executed SQL statements with a large number of buffer gets, to ensure that the execution plans for these SQL statements are optimal.
A,C
D is wrong. Pls see: https://docs.oracle.com/database/121/TGDBA/tune_buffer_cache.htm#TGDBA536
“Repeated scanning of the same large table or index can artificially inflate a low cache hit ratio”
agree with the text, but not what you understand about it.
“Repeated scanning of the same large table or index can artificially inflate a low cache hit ratio” means D is true.
A,C
imo, C and D are correct.
A is wrong because high ratio value NOT necessarily an indication of buffer cache adequately sized. DBA can run the same query over and over and buffer cache hit ratio would increase.
D is correct because “Repeated scanning of the same large table or index can artificially inflate a low cache hit ratio” . That is exactly what D states.
C,D
A means no necessarily
B is a joke
E is a trap.. not complete => creating a keep in a 2mb buffer cache would not help
after reading https://docs.oracle.com/database/121/TGDBA/tune_buffer_cache.htm#TGDBA536
i would say:
Repeated scanning of the same large table or index can artificially inflate a low cache hit ratio => D is true
Do not continuously increase the buffer cache size. => C is true.
So C, D