ORA-27090 - Unable to Reserve Kernel Resources for Asynchronous Disk I/O

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

In this Document

Symptoms

Changes

Cause

Solution

References

APPLIES TO:

Oracle Database - Enterprise Edition - Version 10.2.0.4 to 12.2.0.1 [Release 10.2 to 12.2]

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

***Checked for relevance on 02-Sep-2016***

Oracle Server Enterprise Edition - Version: 10.2.0.4

10.2.0.4

***Checked for relevance on 26-AUG-2014***

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

-------------------------------------

NOTE:

Per bug Bug 13554729 - CORRECT FS.AIO-MAX-NR = 3145728

the published limit in the Oracle Documentation at http://docs.oracle.com/cd/E11882 ... 26/toc.htm#BHCCADGD is incorrect.

The Oracle documentation lists the minimum value as the max value.