今天expdp导出时卡死不跟踪文件中出现类似下面的错误内容：
WARNING:Could not increase the asynch I/O limit to 3328 for SQL direct I/O. It is set to 128
是oracle的BUG，编号：9949948，只发生在10.2.0.5.0和11.2.0.1.0，解决方法有2种，一种是在操作系统层面修改相关参数另一种方法就是打补丁
MOS上的相关内容为：Warning:Could Not Increase The Asynch I/O Limit To XX For Sql Direct I/O [ID 1302633.1]
In this Document
#SYMPTOM”>Symptoms
#CAUSE”>Cause
#FIX”>Solution
#REF”>References
Applies to:
Oracle Server – Enterprise Edition – Version:
10.2.0.5 and
later [Release:
10.2 and later ]
Generic Linux
disk_asynch_io = TRUE
filesystemio_options = none
[root@hnz ~]# cat /proc/sys/fs/aio-max-size
cat: /proc/sys/fs/aio-max-size: No such file or directory
[root@hnz ~]# cat /proc/sys/fs/aio-max-nr
65536
Solution
The aio-max-size kernel parameter doesn’t exist in the 2.6.x Linux
kernels.
This feature is now “automatic” in the 2.6.x kernel, based on the
physical capabilities of the disk device driver.
This should mean that the Linux Kernel is ready to perform ASYNC
I/O.
All install requirements should be met.
To ensure ASYNC I/O can be performed by Oracle Database you need to
verify or set the following parameters in the Database:
sql>alter system set disk_asynch_io=true scope=spfile;
sql> alter system set filesystemio_options=setall scope=spfile;
Then shutdown and startup the database and check if the warning
reappears.
An HCVE report (refer to Note 250262.1) should report no remaining
issues
If the above doesn’t resolve the problem, then increase
fs.aio-max-nr
References
BUG:10334897 –
COULD NOT INCREASE THE ASYNCH I/O LIMIT TO NNN FOR SQL DIRECT I/O.
IT IS SET TO
BUG:9772888 – WARNING:COULD NOT LOWER THE
ASYNCH I/O LIMIT TO 160 FOR SQL DIRECT I/O. IT IS SE
NOTE:205259.1 – Howto Enable Asynchoronous I/O
on Red Hat Linux 2.1
NOTE:225751.1 – Asynchronous I/O (aio) on
RedHat Advanced Server 2.1 and RedHat Enterprise Linux 3
检查相关内容，
[oracle@hnz ~]$ sqlplus /as sysdba
SQL*Plus: Release 10.2.0.5.0 – Production on Sat Oct 22
15:57:01 2013
Copyright (c) 1982, 2010, Oracle. All Rights
Reserved.
Connected to:
Oracle Database
10g Enterprise Edition Release 10.2.0.5.0 – 64bit
Production
With the Partitioning, OLAP, Data Mining and Real Application
Testing options
SQL> show parameter disk_asynch_io
NAME TYPE VALUE
———————————— ———– ——————————
disk_asynch_io boolean TRUE
SQL> show parameter filesystemio_options
NAME TYPE VALUE
———————————— ———– ——————————
filesystemio_options string none
SQL>
SQL> alter system set filesystemio_options=setall scope=spfile;
修改内核参数的值：aio-max-nr设置太低，推荐设置为fs.aio-max-nr= 3145728。修改参数使用/sbin/sysctl -p重新加载参数后，重启数据库即可