RE: Move table online and update the indexes at the same time.
- From: Alexandre Gorbatchev <agorbatchev@xxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Tue, 27 Jul 2004 12:10:10 +0200
I've got couple Metalink notes on dbms_redefinition package. They explain
limitations and there is also some info in the docs as well. If someone is
interested - 177407.1 and 149564.1.
To change storage parameters for new blocks it's enough to change it right
away, but obviously we need to go further. ASSM has several nasty bugs
with LOBs and that's what we've got. However, can you elaborate on ASSM
not suitable for heavy load tables?
Sorry for possible confusion, but saying "wrong tablespace" I didn't mean
just fancy naming. It's IO distribution problem.
Regards,
Alex
From: Wolfson Larry - lwolfs <lawrence.wolfson@xxxxxxxxxx>@freelists.org
on 27-07-2004 02:04 EST
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RE: Move table online and update the indexes at the same time.
Alex, do you have table monitoring on? That is, do you know exactly
what's
happening to these tables?
You'd need lock at end when you're doing rename.
You can change the storage clause for new blocks at least. If this is
heavy
hitter, as you say, you may not want ASSM. Not sure why tables are in
wrong
tablespace, but I'd find something more productive to do if that's only
reason.
Larry
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Alexandre Gorbatchev
Sent: Tuesday, July 27, 2004 12:49 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: Re: Move table online and update the indexes at the same time.
We would definitely test it properly before doing in production but just
wanted to know where the possible problems are.
By the way, when is the lock required - in the beginning or in the end?
I move the table for several reasons:
1.) CREATE TABLE ... AS SELECT produces the table which is much smaller
(sometimes 2-3 times). We are trying to reduce the space usage with it. So
it seems the tables are space.
2.) Change storage clause - FREELIST, FREELIST GROUP or move to ASSM (not
sure, because it seems there are several bugs that we might hit in our
environment)
3.) Physical layout reorganization. Some tables are in wrong tablespaces.
Thanks for your help.
Alex
From: Tanel Poder <tanel.poder.003@xxxxxxx>@freelists.org on 27-07-2004
01:36 ZE3
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Re: Move table online and update the indexes at the same time.
> Tanel,
> Thanks for the reply.
> It's 9i. I thought about table redefinition but I am not sure how it
> affect the performance. Second, I wonder if there a need to get a lock
on
> the table just for a split of a second. We do not have any chance
locking
> the table since there are always several transactions using it.
> What is your experience? Since it appeared only in 9i I am a bit worried
> about using it.
I've never used it in production myself, but as much I've heard, it does
have its problems and limitations - thus extensive testing would be
needed.
It will increase your load, since it basically creates a materialized view
log for your table (and you have to clone the table manually + build the
indexes + apply the changes incrementally later on).
Redefinition package will require a lock for short time on your table if
used properly. The temporary locking could be implemented by deferring
your
transactions for a short time if possible and/or having a tight pl/sql
loop
which retries the operation until it succeeds.
Btw, in 10g there is a "ddl_wait_for_locks" parameter which you can set to
true on your session level - that way Oracle will execute DDL commands in
wait mode, thus waiting until all incompatible locks on given object are
released, instead of erroring out immediately.
Btw, why are you trying to move your tables?
Tanel.
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