近期发现，因数据库监控指标采集比较频繁，甚至触发等待。
解决方案如下：
1、调整采集周期。现行的10S采集频率太高。
2、优化表空间查询语句。
3、考虑回收站原因：
3.1：查询回收站大小：
SYS@evansdb2> SELECT count(*) FROM dba_recyclebin;
COUNT(*)
127
SYS@evansdb2> SELECT value FROM v$parameter WHERE name = 'recyclebin';
VALUE
OFF
3.3：清空全库回收站
SYS@evansdb2> purge DBA_RECYCLEBIN;
DBA Recyclebin purged.
3.4 再次查询回收站大小：
SYS@evansdb2> SELECT count(*) FROM dba_recyclebin;
COUNT(*)
0
3.5 再次查询回收站大小：
SYS@evansdb2> SELECT count(*) FROM dba_recyclebin;
COUNT(*)
0
3.6 收集统计信息：
SYS@evansdb2> exec dbms_stats.gather_table_stats(ownname => 'SYS',tabname => 'RECYCLEBIN$', estimate_percent => 100, method_opt=> 'for all indexed columns',degree=>8);
PL/SQL procedure successfully completed.
3.7 重新查询表空间使用率
SYS@evansdb2> set linesize 200 pagesize 999 long 20000
set timi on ti on
col name format a30
col contents format a9
col extent_management format a8
col size_mb format a12
col Used_MB format a12
col free_mb format a12
col "Used%" format a8
col dt format a20
SELECT d.tablespace_name Name,
d.status,
d.contents,
d.extent_management,
d.segment_space_management,
a.file_cnt,
TO_CHAR(NVL(a.bytes/1048576, 0), '999G999G999') SIZE_MB,
TO_CHAR(DECODE(d.contents,'UNDO',NVL(u.bytes, 0)/1048576,NVL(a.bytes - NVL(f.bytes, 0), 0)/1048576),'999G999G999') Used_MB,
TO_CHAR(DECODE(d.contents,'UNDO',NVL(a.bytes - NVL(u.bytes, 0), 0)/1048576,NVL(f.bytes, 0)/1048576), '999G999G999') FREE_MB,
TO_CHAR(DECODE(d.contents,'UNDO',NVL(u.bytes/a.bytes * 100, 0),NVL((a.bytes - NVL(f.bytes, 0))/a.bytes * 100, 0)),'990D00') "Used%",
TO_CHAR(sysdate, 'yyyy-mm-dd hh24:mi:ss') dt
FROM sys.dba_tablespaces d,
(SELECT tablespace_name, SUM(bytes) bytes, COUNT(file_id) file_cnt
from dba_data_files
GROUP BY tablespace_name) a,
(select tablespace_name, sum(bytes) bytes
from dba_free_space
group by tablespace_name) f,
(SELECT tablespace_name, SUM(bytes) bytes
FROM (SELECT tablespace_name, sum(bytes) bytes, status
from dba_undo_extents
WHERE status = 'ACTIVE'
group by tablespace_name, status
UNION ALL
SELECT tablespace_name, sum(bytes) bytes, status
from dba_undo_extents
WHERE status = 'UNEXPIRED'
group by tablespace_name, status)
group by tablespace_name) u
WHERE d.tablespace_name = a.tablespace_name(+)
AND d.tablespace_name = f.tablespace_name(+)
AND d.tablespace_name = u.tablespace_name(+)
AND NOT (d.extent_management = 'LOCAL' AND d.contents = 'TEMPORARY')
UNION ALL
SELECT d.tablespace_name,
d.status,
d.contents,
d.extent_management,
d.segment_space_management,
a.file_cnt,
TO_CHAR(NVL(a.bytes/1048576, 0), '999G999G999') SIZE_MB,
TO_CHAR(NVL(t.bytes, 0)/1048576, '999G999G999') Used_MB,
TO_CHAR((NVL(a.bytes, 0)/1048576 - NVL(t.bytes, 0)/1048576),'999G999G999') FREE_MB,
TO_CHAR(NVL(t.bytes/a.bytes * 100, 0), '990D00') "Used%",
TO_CHAR(sysdate, 'yyyy-mm-dd hh24:mi:ss') dt
FROM sys.dba_tablespaces d,
(select tablespace_name, sum(bytes) bytes, count(file_id) file_cnt
from dba_temp_files
group by tablespace_name) a,
(select ss.tablespace_name,
sum((ss.used_blocks * ts.blocksize)) bytes
from gvsort_segment ss, sys.ts ts
where ss.tablespace_name = ts.name
group by ss.tablespace_name) t
WHERE d.tablespace_name = a.tablespace_name(+)
AND d.tablespace_name = t.tablespace_name(+)
AND d.extent_management = 'LOCAL'
AND d.contents = 'TEMPORARY'
ORDER BY "Used%";