ADSM-L

Re: Client backup to 3590 tape directly

1998-09-28 11:04:38
Subject: Re: Client backup to 3590 tape directly
From: Steven P Roder <tkssteve AT REXX.ACSU.BUFFALO DOT EDU>
Date: Mon, 28 Sep 1998 11:04:38 -0400
On Mon, 28 Sep 1998, Eric Tang wrote:
> I have a few questions regarding Unix ADSM client backup (& oracle db by
> sql-backtrack or RMAN+ADSMConnectAgent) directly to 3590 tape
> (collocation=yes), in particular how does ADSM handle the backup at
> end-of-tape?
>
> Eg, If a 1GB file is to be backed up and there is a tape with status
> "filling" (only 100MB capacity left) & many scratch tape, will
> i) ADSM split the file into 2, the first 100MB to the "filling" tape and
> the rest to a scratch? Or
> ii) Firstly, ADSM determines 100MB is not enough and mounts a scratch right
> at the beginning?  Or
> iii) other mechanism
>
> If ii) is the answer, question:
> a)  how does adsm determine filesize if client compression is on?
> b) for RMAN/ConnectAgent, there is environment variable DSMO_AVG_SIZE to
> tell ADSM the filesize, is there a similar parameter in SQL-Backtrack?

My experience is that it writes to the current filling tape until it hits
EOT, and then the backup fails with that wonderfull "Internal Server
error detected", or some such verbage.  Your ii) will NOT happen with
collocation, as ADSM will not open a new tape until the previous one is
marked FULL, even if you have mulitple backup streams running for that
client (I find this very annoying).   What I find to then happen is that
migration fills the tape, and the next backup of the client succeeds.

Basically, IMHO, ADSM has a bug handling EOT conditions during client
backups directly to tape.

I have complained multiple times on this list about this bug/behaviour,
without a word out of IBM.  I guess it's time to open an ETR on IBMLink
for this.

Steve (unVMix Systems Programmer/Dude) Roder
(tkssteve AT ubvm.cc.buffalo DOT edu | tkssteve AT acsu.buffalo DOT edu | 
(716)645-3564 ,
   | http://ubvm.cc.buffalo.edu/~tkssteve)
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