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

Troubleshooting


Problem

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.

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Document Information

Modified date:
16 June 2018

UID

swg21138073

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