db file scattered read 定位

最新推荐文章于 2024-03-19 11:16:37 发布

iteye_18798

最新推荐文章于 2024-03-19 11:16:37 发布

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文章标签： Oracle UP Cache

本文链接：https://blog.youkuaiyun.com/iteye_18798/article/details/81994156

**现有系统，查看等待事件的时候，头几个有：DB FILE SCATTERED READ 。

DB FILE SCATTERED READ

The db file scattered read wait event is similar to the db file sequential read, except that the session is waiting for a multi-block I/O read request to complete. The db file scattered read waits are associated with full table scans and index fast full scans (FFS) operations. Oracle reads a set of contiguous blocks up to DB_FILE_MULTIBLOCK_READ_COUNT and scatters them into the Buffer Cache.

1. 找出用户下的全表扫描
select * from v$session_longops where username = 'GSIMS';

193 rows selected.

2.找出具体的表

SELECT distinct target FROM v$session_longops WHERE username = 'GSIMS' ;

TARGET
----------------------------------------------------------------
GSIMS.B_CONTRACT_L
GSIMS.B_CONTRACT
GSIMS.S_LOGACTION
GSIMS.B_REPORT_05
GSIMS.B_REPORT_UNION
GSIMS.B_REPORT_08
GSIMS.B_REPORT_09
GSIMS.B_REPORT_04

8 rows selected.

针对这个问题，调整下：

(1). DB_FILE_MULTIBLOCK_READ_COUNT
(2). 调整表扫描