Well, it doesn't appear to be possible to use /dev/null:

**************************


tlaporte@judas 1% ls -l /dev/null
crw-rw-rw-   1 root     system     2,  2 Mar 06 15:12 /dev/null

adsm> def devc nullfile devt=file
ANR2203I Device class NULLFILE defined.

adsm> def stg nullpool disk
ANR2200I Storage pool NULLPOOL defined (device class DISK).

adsm> def vol nullpool /dev/null
ANR2404E DEFINE VOLUME: Volume /dev/null is not available.
ANS8001I Return code 14.


**************************

Nor does not appear to be possible to mimic the behavior by
using a named pipe:

tlaporte@judas 16% mkfifo -m +rw /tmp/mynull
tlaporte@judas 17% nohup cat < /tmp/mynull > /dev/null &
[1] 16742
tlaporte@judas 18% dsmadmc
ADSTAR Distributed Storage Manager
Command Line Administrative Interface - Version 3, Release 1, Level 0.6
(C) Copyright IBM Corporation, 1990, 1997, All Rights Reserved.

Enter your user id:  tlaporte

Enter your password:

Session established with server DLADSM: AIX-RS/6000
  Server Version 3, Release 1, Level 1.5
  Server date/time: 03/06/00   15:22:40  Last access: 03/06/00   15:09:53


adsm> def vol nullpool /tmp/mynull
ANR2404E DEFINE VOLUME: Volume /tmp/mynull is not available.
ANS8001I Return code 14.



On Mon, 6 Mar 2000, Bill Smoldt wrote:

>John,
>
>To take the tape drives out of the equation, you can create a file device
>class and back up to a disk directory.
>
>To understand where the time is spent on backups, however, you can turn on
>tracing to see the breakdown of operations.
>
>I'd still like to know the direct answer to your question, however.  There
>are times I'd like to be able to run a test backup to the null device.  It's
>a bit dangerous - you might forget and leave your backup directed there . .
>.
>
>Bill Smoldt    SSSI
>Storage Solutions Specialists, Inc.
>
>
> -----Original Message-----
>From:   ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU]  On 
>Behalf Of
>John Schneider
>Sent:   Monday, March 06, 2000 10:42 AM
>To:     ADSM-L AT VM.MARIST DOT EDU
>Subject:        How do I backup to /dev/null?
>
>Greetings,
>
>Is it possible to configure TSM to backup to /dev/null under AIX?  The
>reason I want to do this is I want to remove the performance of the tape
>drive units from the rest of the TSM performance.  If the backup can go
>directly to /dev/null, then the tape drive speed isn't slowing things
>down.
>
>The speed of the database backup software, SQLBackTrack and Oracle,
>drive contention, load on the system, etc. all are part of the
>equation.  I have a customer who is considering upgrading to faster tape
>technology to speed up their backups, but how do we know for sure if
>that is where the bottle neck is?  Typically the network would be, but
>in this case the server and the client are on the same machine.
>
>I figure that if we could backup to /dev/null, then we can see what the
>raw throughput of the rest of pipeline is, and that way we know if
>faster tapes will help.
>
>Any suggestions, including a completely better way to solve this
>problem, are appreciated.
>
>John Schneider
>
>***********************************************************************
>* John D. Schneider   Email: jdschn AT attglobal DOT net * Phone: 636-349-4556
>* Lowery Systems, Inc.
>* 1329 Horan                  Disclaimer: Opinions expressed here are
>* Fenton, MO 63026                   mine and mine alone.
>***********************************************************************
>