遇到direct path sync等待事件

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 遇到direct path sync等待事件

在使用hvr测试 大表同步的时候，遇到direct path sync等待事件，经过查询官方文档，http://docs.oracle.com/cd/E11882_01/server.112/e40402/waitevents003.htm#REFRN00538
有说明如下：

direct path sync

During Direct Path write operations the data is asynchronously written to the database files. At some point the session needs to ensure that all outstanding asynchronous I/O have been completed to disk. On Unix the fsync command, which synchronizes data to disk, is issued to confirm that all the writes have completed and the data is all on disk.

Wait Time: The time taken for the fsync operation to complete, which normally is the time taken to complete the outstanding I/Os.

看上面的说明，是在等待“fsync操作写完毕”的等待时间。

额外说一句：
该等待事件是从10.2.0.5开始有的，如下是测试：

Microsoft Windows [版本 6.1.7600]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

C:\Users\Administrator>f:

F:\>cd oracle\product\10.2.0\db_1\BIN

F:\oracle\product\10.2.0\db_1\BIN>set oracle_sid=fs
F:\oracle\product\10.2.0\db_1\BIN>net start oracleservicefs
OracleServiceFS 服务正在启动 ..................
OracleServiceFS 服务已经启动成功。


F:\oracle\product\10.2.0\db_1\BIN>sqlplus / as sysdba

SQL*Plus: Release 10.2.0.4.0 - Production on Sat May 30 21:30:02 2015 ------>10.2.0.4

Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
21:30:58 sys@FS> col name format a30
21:31:05 sys@FS> col wait_class format a30
21:31:20 sys@FS> select name,wait_class from v$event_name where name like '%direct path%';

NAME                           WAIT_CLASS
------------------------------ ------------------------------
direct path read               User I/O
direct path read temp          User I/O
direct path write              User I/O
direct path write temp         User I/O

Elapsed: 00:00:00.00
21:31:21 sys@FS>

[oracle@lei1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.5.0 - Production on Sun May 31 05:37:11 2015

Copyright (c) 1982, 2010, Oracle.  All Rights Reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production ---------->10.2.0.5
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> set line 200
SQL> col name format a30
SQL> col wait_class format a30
SQL> select name,wait_class from v$event_name where name like '%direct path%';

NAME                           WAIT_CLASS
------------------------------ ------------------------------
direct path sync               User I/O     ------------------->有此等待事件
direct path read               User I/O
direct path read temp          User I/O
direct path write              User I/O
direct path write temp         User I/O

SQL> 

遇到direct path sync等待事件

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原文地址：http://blog.csdn.net/msdnchina/article/details/46278549