创建Latch快照表
CREATE TABLE snap_latch as
SELECT 0 snap_id, sysdate snap_date, a.*
 FROM V$LATCH a;
 ALTER TABLE snap_latch add
   (constraint snap_filestat primary key (snap_id, name));

定期insert数据
INSERT INTO snap_latch
SELECT 1, sysdate, a.* FROM V$LATCH a;


查询Latch
SET LIN 120
SET PAGES 60
SET NUMFORMAT 999999.9   


SELECT SUBSTR(a.name,1,20) NAME, (a.gets-b.gets)/1000 "Gets(K)",
       (a.gets-b.gets)/(86400*(a.snap_date-b.snap_date)) "Get/s",
       DECODE ((a.gets-b.gets), 0, 0, (100*(a.misses-b.misses)/(a.gets-b.gets))) MISS,
       DECODE ((a.misses-b.misses), 0, 0,
              (100*(a.spin_gets-b.spin_gets)/(a.misses-b.misses))) SPIN,
      (a.immediate_gets-b.immediate_gets)/1000 "Iget(K)",
       (a.immediate_gets-b.immediate_gets)/ (86400*(a.snap_date-b.snap_date)) "IGet/s",
       DECODE ((a.immediate_gets-b.immediate_gets), 0, 0,
       (100*(a.immediate_misses-b.immediate_misses)/ (a.immediate_gets-b.immediate_gets))) IMISS
  FROM snap_latch a, snap_latch b
  WHERE a.name = b.name
 AND a.snap_id = b.snap_id + 1
   AND ( (a.misses-b.misses) > 0.001*(a.gets-b.gets)
       or (a.immediate_misses-b.immediate_misses) > 0.001*(a.immediate_gets-b.immediate_gets))
ORDER BY 2 DESC;