解决db file sequential read与db file scattered read

1.根据收集的等待事件，分析是那些对象以及对应的sql。

2.确定是那些对象，执行如下：

SELECT segment_name, partition_name, p1, p2
FROM dba_extents, wait1
WHERE wait1.p2 BETWEEN block_id AND (block_id + blocks - 1)
AND file_id = wait1.p1
ORDER BY segment_name

3.确定执行的sql语句，执行如下：

SELECT hash_value, address, piece, sql_text
FROM v$sqltext
WHERE hash_value IN (SELECT DISTINCT sql_hash_value
FROM wait1)
ORDER BY hash_value, piece;

SELECT hash_value, address, piece, sql_text
FROM v$sqltext
WHERE hash_value ＝ :1
ORDER BY hash_value, piece;

注意这个有可能一些已经不在shared pool。

4.另外通过这个脚本也可以确定对象，缺点这个块一定要读入sga。

SELECT DISTINCT a.object_name, a.subobject_name
FROM dba_objects a, SYS.x_$bh b
WHERE (a.object_id = b.obj OR a.data_object_id = b.obj)
AND b.file# = :p1
AND b.dbablk = :p2 ；