Viewing the buffer cache hit rate

Sql> Select Name,value from V$sysstat where name in (' db block gets ', ' consistent gets ', ' physical reads ');

NAME VALUE
---------------------------------------------------------------- ----------
DB Block gets 932
Consistent gets 50535
Physical reads 9145

Hit Rate calculation formula

Hit Radio=1-physical reads/(db block gets+consistent gets)

Sql> Select (1-9145/(50535+932)) from dual;

(1-9145/(50535+932))
--------------------
.822313327
Sql> Show Parameter Db_block_buffers

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
Db_block_buffers integer 0

Due to the introduction of the SGA Auto-management in 10G, show parameter found the db_block_buffers to be 0

View current buffer Cache size

Sql> select name, bytes/1024/1024 Mb from v$sgainfo where name = ' Buffer Cache Size ';

NAME MB
-------------------------------- ----------
Buffer Cache Size 288 This buffer cache size refers to the default + keep +recycle and

Sql> select Current_size from V$buffer_pool;

Current_size
------------
288 I do not configure keep pool here, nor do I configure recycle pool

If a long-running database hit radio<90%, you should consider allocating multiple points of memory to the buffer cache, adding physical memory, or SQL tuning

The ideal hit radio should be above 95%

Viewing the buffer cache hit rate