SELECT (1 - (v3.VALUE / (v1.VALUE + v2.VALUE))) * 100
INTO v_cache_hit_ratio
  FROM v$sysstat v1,
  v$sysstat v2,
  v$sysstat v3
 WHERE v1.NAME = 'db block gets'
   AND v2.NAME = 'consistent gets'
   AND v3.NAME = 'physical reads';

SELECT SUM(PINS) / (SUM(PINS) + SUM(RELOADS)) * 100
FROM V$LIBRARYCACHE;

SELECT (SUM(GETS)/(SUM(GETS)+SUM(GETMISSES))) * 100
FROM
V$ROWCACHE;

SELECT ROUND((100 * b.VALUE) /DECODE ((a.VALUE + b.VALUE),
       0,1,(a.VALUE + b.VALUE)),2)
FROM   v$sysstat a,
       v$sysstat b
WHERE  a.name = 'sorts (disk)'
AND    b.name = 'sorts (memory)';

select
a.sid,
a.username,
machine,
program,
cpu_time/1000000 cpu_time,
elapsed_time/1000000 elapsed_time,
sql_text,
rows_processed,
buffer_gets,
disk_reads,
parse_calls,
first_load_time,
fetches,
executions,
loads,
sharable_mem,
persistent_mem,
runtime_mem,
block_gets,
consistent_gets,
physical_reads,
block_changes,
consistent_changes,
sysdate-((4/1440)*60)
from
v$session a,
v$sqlarea b,
v$sess_io c
where
a.sql_hash_value = b.hash_value
and a.sql_address = b.address
and a.sid = c.sid
;

ERROR] [2008-10-02 13:09:31] [JDBCExceptionReporter] The data source returned 
null from getConnection(user,password).
org.hibernate.exception.GenericJDBCException: 
Cannot open connection

Oracle9i Enterprise Edition Release 9.2.0.8.0 - Production
PL/SQL Release 9.2.0.8.0 - Production
CORE    9.2.0.8.0       Production
TNS for Linux: Version 9.2.0.8.0 - Production
NLSRTL Version 9.2.0.8.0 - Production

NAME                      VALUE
-------------------- ----------
Fixed Size               452620
Variable Size        1073741824
Database Buffers      536870912
Redo Buffers            2240512

SQL>