KAIO: out of OS resources, errno = 11 _aiowrite() returning EAGAIN

Technote (troubleshooting)

Problem(Abstract)

This article describes one known cause for the error KAIO: out of OS resources, errno 11

Symptom

You are using IBM Informix® Dynamic Server on the AIX operating system and you find this error in the message log:


KAIO: out of OS resources, errno = 11, pid = 117908 on different Versions of   AIX  *** _aiowrite() returning EAGAIN ***

Cause

Either AIX kernal tuning parameter, maxreqs is set low. Or, the IBM Informix® Dynamic Server's environment variable, IFMX_AIXKAIO_NUM_REQ for maximum number of requests, is set too low for the current I/O load on the system. The default value, if the environment variable is not set, is 1024. 

maxreqs - is AIX kernel tuning parameter which specifies the maximum number of asynchronous I/O requests that can be outstanding at any one time. The default value is 4096.

Resolving the problem

• Set environment variable IFMX_AIXKAIO_NUM_REQ to a higher value. The minimum value is 512 and the maximum value is the Maximum number of requests set for Kernel AIO.
• If Informix AIO is used, increase the number of AIO VP's in the onCONFIG configuration file so I/O will be faster and the queue for AIO control blocks will not overflow.

If the above solutions does not work, refer to the related information section to find how to tune OS kernel.

https://www-304.ibm.com/support/docview.wss?uid=swg21188868