By default, the HPUX version of IDS uses a "select-based" implementation of Kernel AIO (KAIO). This was implemented a long time ago due to an HP performance problem that occurred when the OS kaiopoll function was called with a timeout. This is the default behavior, and is what occurs when IFMX_HPKAIO_VER is not set, or is set to 3.
IFMX_HPKAIO_VER can also be set to 2 when used with HPUX 10.10 and greater, and will cause the engine to use a "flag style" KAIO.
The recommendation is to not set this variable unless you have a non-standard HPUX version number.
AM