IBM Support

Tuning Kernel Asynchronous I/O (KAIO) for IBM Informix on HP-UX

Troubleshooting


Problem

This article goes over the environment variable that can be used to change the default resources used by the engine for Kernel Asynchronous I/O (KAIO) on the HP-UX platform.

Resolving The Problem


PROBLEM

Database performance is poor because of input/output (I/O) requests. The IBM® Informix® Dynamic Server™ message log might display one of these error messages:

      KAIO out of OS resources, errno = 11

    or 
      KAIO out of OS resources, errno = 35

CAUSE

Each time the database server makes a kernel asynchronous input output (KAIO) request, it uses a special operating system structure. A certain number of these structures are allocated when the database server starts and are reused as long the instance is online.

The problem will occur if there are not enough structures available to handle all of the I/O requests made by the database server.


Note: This is only one possible cause for this problem. If this document does not solve your problem, see if other documents exist for the same problem.


SOLUTION

Increase the number of KAIO requests allowed simultaneously by the database server. Do this by increasing the value of the IFMX_HPKAIO_NUM_REQ environment variable.

Set the variable to the desired number at the command line and then shut down and restart the database server.

    Limits of the
    IFMX_HPKAIO_NUM_REQ
    environment variable.
    Minimum Value
    10
    Maximum Value
    5000
    Default Value
    1000

    Note: These values may change in future versions of the operating system or database server.

    Example:
    This example shows how to increase the number of concurrent KAIO requests to 2300 from the default of 1000 using Korn shell:
      $ IFMX_HPKAIO_NUM_REQ=2300
      $ export IFMX_HPKAIO_NUM_REQ

You can also change some operating system kernel parameters for KAIO. If you are still experiencing poor performance, contact your local technical support office.

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Document Information

Modified date:
08 November 2018

UID

swg21142285