又是数据库服务器IO高引起的问题

         昨天整个系统慢，weblogic日志有大量stuck，数据库服务器IO负载高。取了数据库报告后发现了问题。

负载很高，平常DB Time最多1000.

Host Name	Platform	CPUs	Cores	Sockets	Memory (GB)
XXXXXX	AIX-Based Systems (64-bit)	128	32		123.50

	Snap Id	Snap Time	Sessions	Cursors/Session	Instances
Begin Snap:	8940	01-12月-15 13:59:29	1263	114.2	2
End Snap:	8943	01-12月-15 16:19:14	1648	96.0	2
Elapsed:		139.75 (mins)
DB Time:		30,337.56 (mins)

TOP等待事件都是IO

Top 10 Foreground Events by Total Wait Time

Event	Waits	Total Wait Time (sec)	Wait Avg(ms)	% DB time	Wait Class
db file sequential read	19,395,915	512.6K	26	28.2	User I/O
read by other session	9,753,486	385.8K	40	21.2	User I/O
direct path read temp	4,205,461	310.7K	74	17.1	User I/O
direct path read	1,886,691	133.4K	71	7.3	User I/O
DB CPU		86.1K		4.7
direct path write temp	840,182	61.9K	74	3.4	User I/O
gc buffer busy acquire	3,103,568	58.2K	19	3.2	Cluster
db file scattered read	1,721,381	55.1K	32	3.0	User I/O
db file parallel read	859,955	33.5K	39	1.8	User I/O

表XX_PURCHASE_CONTRACT_ITEM_MV物理读非常高，284623132*8/1024/1024=2171.5G的数据，在磁盘上读了这么多数据，当然，这个数字需要*2, 因为是RAC的数据库。

Segments by Physical Reads

• Total Physical Reads: 620,000,121
• Captured Segments account for 52.3% of Total

Owner	Tablespace Name	Object Name	Subobject Name	Obj. Type	Physical Reads	%Total
XXXXX	Www	XX_PURCHASE_CONTRACT_ITEM_MV		TABLE	284,623,132	45.91
XXXXX	Www	XX_PURCHASE_ITEM	P0308	TABLE PARTITION	7,707,543	1.24
XXXXX	Www	XX_PURCHASE_ITEM	P0314	TABLE PARTITION	6,211,667	1.00
XXXXX	Www	XX_PURCHASE_ITEM	P0313	TABLE PARTITION	5,502,512	0.89
XXXXX	Www	XX_PURCHASE_ITEM	P0318	TABLE PARTITION	3,820,804	0.62