解決direct path read 與 direct path write問題

1.這個問題主要與sort有關。

2.确定對象的sql：

SELECT segment_name, partition_name, p1, p2, wait1.sql_hash_value

FROM dba_extents, wait1

WHERE wait1.p2 BETWEEN block_id AND (block_id + blocks - 1)

AND file_id = wait1.p1

AND wait1.event = 'direct path read'

ORDER BY segment_name

3.根據回話讀取的資料庫檔案類型了解回話所做的事情。如果是臨時檔案，則回話正在讀取先前通過direct path write操作的臨時段。如果是資料檔案，可能是并行查詢從屬操作在工作。

SELECT NAME

FROM v$datafile

WHERE file# = :p1

UNION ALL

SELECT a.NAME

FROM v$tempfile a, v$parameter b

WHERE b.NAME = 'db_files' AND a.file# + b.VALUE = :p1

4.如果回話讀取臨時段，要查明是什麼類型的段：

SELECT DISTINCT DECODE (ktssosegt,

1, 'SORT',

2, 'HASH',

3, 'DATA',

4, 'INDEX',

5, 'LOB_DATA',

6, 'LOB_INDEX',

'UNDEFINED'

)

FROM SYS.x$ktsso

WHERE inst_id = USERENV ('instance')

AND ktssoses = :cursor_session_address

AND ktssosno = :cursor_serial# ；

5.擷取sql語句：

SELECT hash_value, address, piece, sql_text

FROM v$sqltext

WHERE hash_value = :1

ORDER BY hash_value, piece;