Tuning Asynchronous-I/O Kernel parameters to avoid error KAIO out of resource on HP-UX

Problem(Abstract)

This article goes over the Operating System Kernel that can be configured to avoid error KAIO out of resource on the HP-UX platform

Resolving the problem

PROBLEM

When using Kernel Asynchronous I/O (KAIO) with IBM Informix Dynamic Servers, you might experience the following message in the database server message log:

KAIO out of resource errno=11
or
KAIO out of resource errno=35

CAUSE 

This error indicates a shortage of KAIO resources. 


SOLUTION 

Tune the KAIO subsystem: 

1. Configure the number of KAIO requests. 

Note: Check Related information for more detail. 

2. Tune the Operating System Kernel parameters. 

Kernel parameter	Description	Minimum	Maximum	Default
aio_listio_max	Specifies how many POSIX asynchronous I/O operations are allowed in a single listio() call.	2	65536	256
aio_max_ops	Specifies the system-wide maximum number of POSIX asynchronous I/O operations that may be queued at any given time.	1	1048576	2048
aio_physmem_pct	Percentage of physical memory that can be locked for use in POSIX asynchronous I/O operations.	5	50	10
aio_prio_delta_max	Maximum delta that a process can decrease its asynchronous I/O priority level	0	20	20
max_async_ports	Maximum number of ports to the asynchronous disk-I/O driver that processes can have open at any given time.	1	2147483647	50

Note:

• All configurable kernel parameters must be specified using an integer value or a formula consisting of a valid integer ｅxpression.

• The maximum and/or default values of certain parameters may change between releases or to vary between 32-bit and 64-bit processors.

Warning: 

Changing kernel parameters to improper or inappropriate values or combinations of values can cause data loss, system panics, or other (possibly very obscure and/or difficult to diagnose) operating anomalies, depending on which parameters are set to what values. 

• Before altering the value of any configurable kernel parameter, be sure you know the implications of making the change.
• Never set any system parameter to a value outside the allowable range for that parameter (SAM refuses to store values outside of the allowable range).
• Many parameters interact, and their values must be selected in a balanced way.

For more information about POSIX asynchronous I/O, see the HP-UX Reference entry aio(5). Please contact HP-UX OS support for more information about these parameters and their management.

http://www-01.ibm.com/support/docview.wss?uid=swg21138073