aio-max-nr :1048576→3145728)，避免触发

ORA-27090 - Unable to Reserve Kernel Resources for Asynchronous Disk I/O (Doc ID 579108.1)

结论：内核参数的值：aio-max-nr设置太低，推荐设置为fs.aio-max-nr= 3145728，但是默认安装的设置是1048576。修改参数后使用/sbin/sysctl -p重新加载参数后，重启数据库即可。

https://support.oracle.com/epmos/faces/DocumentDisplay?_afrLoop=129024659352664&id=579108.1&displayIndex=2&_afrWindowMode=0&_adf.ctrl-state=2vlzgh4wz_56

Oracle Database - Enterprise Edition - Version 10.2.0.4 to 19.14.0.0.0 [Release 10.2 to 19]
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Gen 1 Exadata Cloud at Customer (Oracle Exadata Database Cloud Machine) - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Linux x86-64
Linux x86
Oracle Server Enterprise Edition - Version: 10.2.0.4
10.2.0.4
*** ***



SYMPTOMS
You discover messages of this nature in your alert log:


ORA-27090: Message 27090 not found; product=RDBMS; facility=ORA

Additional information: 3
Additional information: 128
Additional information: 65536

- OR -



ORA-27090: UNABLE TO RESERVE KERNEL RESOURCES FOR ASYNCHRONOUS DISK I/O

Additional information: 3
Additional information: 128
Additional information: 65536

- OR -


ORA-27090: Message 27090 not found;  product=RDBMS; facility=ORA
Linux-x86_64 Error: 4: Interrupted system call
Additional information: 3
Additional information: 128
Additional information: 65536


Strace against DBWR shows:


io_setup(4096, 0x66e1588) = -1 EAGAIN (Resource temporarily unavailable),

which is related to "aio-max-nr" kernel limit.


CHANGES


CAUSE
The "aio-max-nr" kernel limit is too low.


SOLUTION
The "aio-max-nr" kernel limit should be adjusted according to Oracle recommendations which are available in this document:

Oracle Validated Configuration:
http://linux.oracle.com/pls/apex/f?p=102:2:2007385298933639::NO::P2_VC_ID:426

Also, this parameter should be set as follows:
-------------------------------------
fs.aio-max-nr= 3145728
-------------------------------------

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