I am running the following (Oracle suggested - 8i) query to get the biffer hit ratio.  
This is our production Apps database.  The numbers for logical and physical reads seem 
VERY high (especially phys_reads, which obviously causes our hit ratio to drop to 0).  
What could have caused this?

SQL> list 
  1      select A.value + B.value  "logical_reads",
  2      C.value                   "phys_reads",
  3      D.value                   "phy_writes",
  4  (A.value+B.value)-C.value "log_minus_phys",
  5      round(100 * ((A.value+B.value)-C.value) / (A.value+B.value))
  6         "Buffer Hit Ratio"
  7      from V$SYSSTAT A, V$SYSSTAT B, V$SYSSTAT C, V$SYSSTAT D
  8      where A.statistic# = 38
  9      AND B.statistic# = 39
 10      AND C.statistic# = 40
 11*     AND D.statistic# = 44
SQL> /

               logical_reads                   phys_reads       phy_writes   
log_minus_phys Buffer Hit Ratio
---------------------------- ---------------------------- ---------------- 
---------------- ----------------
  18,446,744,070,414,253,130   18,446,744,069,433,707,559        2,043,488      
980,545,571                0

Here are some other stats;

DTSTAMP                            PHYSICAL_READS    DB_BLOCK_GETS              
CONSISTENT_GETS PHYSICAL_WRITES
-------------------- ---------------------------- ---------------- 
---------------------------- ---------------
       PHYSICAL_READS_DIRECT PHYSICAL_WRITES_DIRECT SESSION_LOGICAL_READS
---------------------------- ---------------------- ---------------------
08-APR-2002 10:35:16   18,446,744,069,434,437,169      171,781,916   
18,446,744,070,280,471,598       2,103,859
  18,446,744,047,946,114,866                966,679         1,032,014,671
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-- 
Author: Glenn Travis
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