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Re: Query results to .csv/use of dblinks

From: Tanel Poder <tanel.poder.003_at_mail.ee>
Date: Tue, 26 Aug 2003 13:29:26 -0800
Message-ID: <F001.005CD528.20030826132926@fatcity.com>


Hi!

In one migration of about 600GB DB I used 2 dblinks (loading different partitions in parallel with separate statements), then added 3rd link after what the bottleneck seemed to be the network. (I saw full network utilization from perfmon on windows, wasn't too much of a wait interface user back then). But your mileage may vary.

So, full hardware utilization is definitely good, at least during migrations, but before thinking about that, you have to put together an optimal migration path and methodology.

Tanel.

> Tanel,
>
> A quick question? How many open dblinks you have used at one time without
> any issues? Default setting in init.ora is 4(if I am not wrong) and I
never
> used it more than that. If Dennis wants to use more than 4 dblinks at one
> time, he should modify this param(open_dblinks) in init.ora, right.
>
> Regards
> Rafiq
>
>
>
>
>
>
>
>
> Reply-To: ORACLE-L_at_fatcity.com
> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> Date: Tue, 26 Aug 2003 09:14:26 -0800
>
> Hi!
>
> What is your goal? To finish data transfer in the shortest time or keep
> hardware utilization maximum during transfer?
> I think you should concentrate on keeping the time for doing data transfer
> low.
>
> Depending on your network - in case of gigabit (or 10 Gb) you could look
at
> enabling jumbo frames, which enable ethernet packets up to 9000 bytes.
Also
> set (SDU=32768) in your listener and tnsnames.oras (you can set it with
> normal 1500 byte frames as well).
>
> About parallellism, you might want to run several bulk inserts over dblink
> to fully utilize your network (fill the "gaps" when one session is busy
> inserting, thus not using the network). But if your source disk array (or
> CPUs) are slow then they might be the bottleneck.
> If you got SAN and a temporary spare server, do a BCV copy or mirror
split,
> open up several clones of a database and copy data from all of them.
>
> Also, when you have SAN, there's no need for network transfer at all - you
> just mount the filesystem with dump/exportfiles on target database and do
> the load from there. If your operating systems are different, then just
dump
> to raw device, with pipe and tar for example, or completely raw,
remembering
> your data sizes. Note that in some (older) operating systems there were
few
> blocks in beginning of device which were used (and written) by operating
> system (Tru64 had the largest I know - 64k). Thus you had to make sure you
> didn't write anything there (oseek=65536 for dd for example).
>
> If downtime isn't an issue for you, it might not be worth trying above
> recommendations, but in RVLDBs (really very large databases) all of this
can
> help a lot.
>
> Tanel.
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Tuesday, August 26, 2003 5:54 PM
>
>
> > Taniel, Binley
> > Thanks for the excellent suggestions.
> > At this point we have been testing with two smaller test systems,
> moving
> > a single table at a time, but initial indications are that the
> performance
> > order is:
> > 1. Perl dump to CSV / ftp / SQL*Loader
> > 2. Copy across database link
> > 3. Export/ ftp / import
> >
> > I need to re-run the tests once the target production system is
available
> to
> > re-confirm which is faster. I am pretty confident in the ability to run
> > multiple SQL*Loader and import sessions simultaneously. I am a little
> > nervous about the ability of the database link to scale to enough
> > simultaneous sessions to keep the RAID sets maxed out on the target
> system.
> > Several years ago when I was doing a large conversion I hit that limit.
> Some
> > days I wonder if we are the beneficiary or victim of our prior
> experience.
> > Oh well thanks for all the good suggestions, on to testing, testing,
> > testing.
> >
> > Dennis Williams
> > DBA, 80%OCP, 100% DBA
> > Lifetouch, Inc.
> > dwilliams_at_lifetouch.com
> >
> >
> > -----Original Message-----
> > Sent: Monday, August 25, 2003 7:09 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > Hi!
> >
> > What about several insert /*+ APPEND NOLOGGING */ commands over
database
> > link run in parallel? (Possibly over dedicated network). This is fast
and
> is
> > easier (in case you don't hit any compatibility problems). If you
happen
> to
> > be running on Windows for some reason, you could try to use named pipes
> > network protocol instead of TCP as well.
> >
> > Tanel.
> >
> > ----- Original Message -----
> > To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> > Sent: Monday, August 25, 2003 11:04 PM
> >
> >
> > > Thanks Tanel
> > > We will undoubtedly use export/import for the many small tables. We
> are
> > > looking for alternatives that will perform even faster. The insert
> phase
> > > seems to be the slowest part, and that is where SQL*Loader in direct
> path
> > > really shines. Now the next issue is how to produce a CSV file as
fast
> as
> > > possible, and so far it looks like Jared's Perl program is the clear
> > winner.
> > >
> > > Dennis Williams
> > > DBA, 80%OCP, 100% DBA
> > > Lifetouch, Inc.
> > > dwilliams_at_lifetouch.com
> > >
> > >
> > > -----Original Message-----
> > > Sent: Monday, August 25, 2003 1:05 PM
> > > To: Multiple recipients of list ORACLE-L
> > >
> > >
> > > Hi!
> > >
> > > Spooling from sqlplus is VERY slow.
> > > Is the source database Oracle? Then use export/import
> > > If not, is there an ODBC driver for source database? Then use Oracle
> > > heterogenous services and do your transfer directly, without any
> > > intermediate files.
> > > Or use some very expensive software for doing this simple job...
> > >
> > > Tanel.
> > > P.S. if you definitely want to spool to textfile fast, Sparky could
be
> > what
> > > you want...
> > >
> > > ----- Original Message -----
> > > To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> > > Sent: Monday, August 25, 2003 7:24 PM
> > >
> > >
> > > > Jared - Thanks for posting this. At the moment, we are preparing to
> move
> > > > large database to a new server. Based on the advice you posted
> several
> > > > months ago, we have been testing SQL*Loader and as you predicted,
it
> is
> >
> > > > indeed fast. But also as you predicted, using SQL*Plus to create a
> CSV
> > > isn't
> > > > very fast. Am I correct in assuming the dump.sql will not be the
best
> > > choice
> > > > for large tables? We are installing perl since you mentioned that
> would
> > > > probably be much faster.
> > > >
> > > > Dennis Williams
> > > > DBA, 80%OCP, 100% DBA
> > > > Lifetouch, Inc.
> > > > dwilliams_at_lifetouch.com
> > > >
> > > >
> > > > -----Original Message-----
> > > > Sent: Monday, August 25, 2003 9:40 AM
> > > > To: Multiple recipients of list ORACLE-L
> > > >
> > > >
> > > > http://www.cybcon.com/~jkstill/util/dump/dump.html
> > > >
> > > > On Mon, 2003-08-25 at 05:39, Imran Ashraf wrote:
> > > > > Hi,
> > > > >
> > > > > Whats the best way to write the results of a SQL query to a CSV
> file?
> > > > >
> > > > > Thanks.
> > > > >
> > > > > _________________________________________________________________
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> > > > >
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> > > Author: Tanel Poder
> > > INET: tanel.poder.003_at_mail.ee
> > >
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> > Author: Tanel Poder
> > INET: tanel.poder.003_at_mail.ee
> >
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> Author: Tanel Poder
> INET: tanel.poder.003_at_mail.ee
>
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> Author: M Rafiq
> INET: rafiq9857_at_hotmail.com
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Tanel Poder
  INET: tanel.poder.003_at_mail.ee

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Received on Tue Aug 26 2003 - 16:29:26 CDT

Original text of this message

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