aio_max_ops(5)                                               aio_max_ops(5)
                          Tunable Kernel Parameters



 NAME    [Toc]    [Back]
      aio_max_ops - maximum number of POSIX async I/O operations that can be
      queued at any time

 VALUES    [Toc]    [Back]
    Failsafe
      2048

    Default    [Toc]    [Back]
      2048

    Allowed values    [Toc]    [Back]
      The minimum value allowed is 2.  The maximum value allowed is
      0x100000.  The value is further constrained in that it must be greater
      than or equal to aio_listio_max.

      Specify a positive integer value.

 DESCRIPTION    [Toc]    [Back]
      This parameter places a limit on the system resources that can be
      consumed if large numbers of POSIX asynchronous I/O operations are
      queued on the system at the same time.  This parameter limits the
      ability of competing processes to overwhelm the system with large
      numbers of asynchronous I/O operations and the memory they require.

      Each enqueued asynchronous operation requires allocation of system
      memory for its internal control structure, thus making this limit
      necessary.  In addition to the system-wide limit, there is a perprocess
 limit that is controlled using the argument RLIMIT_AIO_OPS to
      getrlimit() and setrlimit() calls.

      aio_listio_max limits the number of operations that can be contained
      in a single listio() call from a given process, and the value of
      aio_max_ops must be sufficient to meet the reasonable needs of all
      processes that are making simultaneous or nearly simultaneous listio()
      calls without jeopardizing overall system balance.

    Who Is Expected to Change This Tunable?
      System administrators that run applications requiring heavy usage of
      POSIX AIO to file systems.

    Restrictions on Changing    [Toc]    [Back]
      This tunable is dynamic (tuning will take effect immediately on the
      running system).

    What Other Tunables Should Be Changed at the Same Time as This One?
      The value assigned to aio_max_ops must be greater than or equal to
      aio_listio_max.

 WARNINGS    [Toc]    [Back]
      All HP-UX kernel tunable parameters are release specific.  This



 Hewlett-Packard Company            - 1 -      HP-UX 11i Version 2: Sep 2004






 aio_max_ops(5)                                               aio_max_ops(5)
                          Tunable Kernel Parameters



      parameter may be removed or have its meaning changed in future
      releases of HP-UX.

      Installation of optional kernel software, from HP or other vendors,
      may cause changes to tunable parameter values.  After installation,
      some tunable parameters may no longer be at the default or recommended
      values.  For information about the effects of installation on tunable
      values, consult the documentation for the kernel software being
      installed. For information about optional kernel software that was
      factory installed on your system, see HP-UX Release Notes at
      http://docs.hp.com.

 AUTHOR    [Toc]    [Back]
      aio_max_ops was developed by HP.

 SEE ALSO    [Toc]    [Back]
      kctune(1M), sam(1M), gettune(2), settune(2), getrlimit(2),
      setrlimit(2), aio(5), aio_listio_max(5).


 Hewlett-Packard Company            - 2 -      HP-UX 11i Version 2: Sep 2004