Async I/O on HP-UX

[Trojan36]

Does anyone know if all the version of HP-UX supports the Async I/O driver? Also, what's the implications of using raw partitions with Async I/O vs using filesystem in an Oracle DB environment?

thx in advance

[Steven E. Protter]

Shalom,

All versions of HP-UX support async i/o?

No.

All supported versions, 11.11, 11.23, 11.31 do support async i/o on cooked file systems and raw disk.

Raw disk used to offer a 10% performance advantage, however testing done in 2006 by A Clay Stephenson indicate that advantage has dwindled.

Backup and management is easier on cooked file systems.

SEP

[Wim Rombauts]

And I learned that usage of async IO is not automatic on HP-UX. The oracle user needs to have rw access to /dev/async nad has to have the MLOCK privilege (put line "oracle MLOCK in /etc/privgroup).

This last could be because we have RBAC installed (but not effectively used) and the database runs within a secured compartment.

[Trojan36]

Hi Steven,

Do you have information how to set up async I/O on filesystems as it relates to setting it up with Oracle database processing? Weâ re having issues in commit processing where Itâ s take quite a bit of time to write log buffers to redologs which is causing considerable application wait.

This would be 11.23 on Itanium.

Thx in advance

[Duncan Edmonstone]

SEP won't have any information on async IO on HPUX filesystems for Oracle, cos its not possible for Oracle... I suggest you take a look at metalink article 139272.1

We will support VxFS concurrent IO on the 0909 release of 11.31 via a patch in the Nov/Dec timeframe which may help in your scenario if you are on 11.31.

In the meantime, you should ensure that your online redo logs are on seperate filesystems from your datafiles (and ideally seperate disks) and that the filesystem has a 1K block size to avoid unaligned writes (fstyp -v on the filesystem should have "f_frsize: 1024")

If you have OnlineJFS for the redo log filesystems you should also use the following mount options:

delaylog,nodatainlog,convosync=direct,mincache=direct

HTH

Duncan

[Duncan Edmonstone]

... and I just noted your on 11.23, so just think about your mount options...

HTH

Duncan