缓冲区高速缓存的命中率 的定义是什么？
缓冲区高速缓存的命中率 的定义是什么？正常为多少？命中率=1-(physical reads/(db blockgets+consistent gets)
其中：
db block gets 数据请求总数
consistent gets 存取所满足要求的请求
physical reads 造成对磁盘上数据文件存取的数据请求总数
还是：
------看内存缓冲区使用效率的指数是命中率HITS:
Hits=Logical_reads/(logical_reads+physical_reads)
其中：logical_reads=db_block_gets+consistent_reads
彷徨呀！
缓冲区高速缓存的命中率 的定义是什么？
计算系统的瓶竟一般在I/O系统，为了提高系统处理速度，系统提前将数据读入一块内存区，叫高速缓存，但提前读入的数据未必就是需要的，着就是命中率 。缓冲区高速缓存的命中率 的定义是什么？
那怎么能提高命中率呢？缓冲区高速缓存的命中率 的定义是什么？
可以调整db_cache_size的大小或起用多个cache_buffer 如：db_keep_cache_size
db_recycle_cache_size
缓冲区高速缓存的命中率 的定义是什么？
我想知道它的确切计算公式是什么？正常的取值范围？哥哥！缓冲区高速缓存的命中率 的定义是什么？
总结如下：命中率=1-(physical reads/(db blockgets+consistent gets)
上面的定义是正确的！其中：
consistent gets ：
This statistics reports the number of blocks requested in consistent mode. Blocks are requested in consistent mode for consistent read operations. When a block is requested in consistent mode, if any changes have been committed or made to that block since the requesting statement (or transaction) began, then they must be rolled back for the purposes of the read, to give a consistent view of the data at that time.
db block gets ：
This statistics counts the number of blocks requested in current mode. Blocks are requested in current mode in order to be changed.
physical reads ：
This is the number of database blocks that the database instance has requested the operating system to read from disk. This is typically greater than the actual number of disk read operations performed because of multiblock reads and because some read requests may be satisfied from the operating system buffer cache
但命中率取值：
Calculate buffer cache hit ratio in the database. Make sure it is more than 80 for an oltp environment and 99 is the best value. good ,thanks
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