Oracle Database Discussions

Using: Oracle 10.2.0.1.0, Redhat 4, 64bit.

Manual calculation of ‘Buffer Cache hit ratio’ is very off from what it shown in statspack.

Statspack shows:

Instance Efficiency Percentages
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            Buffer Nowait %:  100.00       Redo NoWait %:   99.97
            Buffer  Hit   %:   99.18    In-memory Sort %:  100.00
            Library Hit   %:   90.43        Soft Parse %:   52.56
         Execute to Parse %:   80.14         Latch Hit %:   99.98
Parse CPU to Parse Elapsd %:   96.21     % Non-Parse CPU:   56.89

Manual calculation (Got this formula from Sybex PT book, page 275):

SQL> select name, 1-(PHYSICAL_READS/(DB_BLOCK_GETS+CONSISTENT_GETS)) 
from  v$buffer_pool_statistics;
NAME                 1-(PHYSICAL_READS/(DB_BLOCK_GETS+CONSISTENT_GETS))
-------------------- --------------------------------------------------
DEFAULT                                                      .700247215

Any idea, why using v$buffer_pool_statistics gives wrong results?

Thanks regards,