Re: options for read only mirror with 10g SE or SE One
- From: Carel-Jan Engel <cjpengel.dbalert@xxxxxxxxx>
- To: identd@xxxxxxxxx
- Date: Mon, 27 Sep 2004 21:13:32 +0200
This discussion is diverting somewhat from what the Original Poster was
asking for.
Standby in all appearances (except Logical Standby, but that is EE)
tends to be in recovery mode. So, there is quite few read-only access
possible to the second database, which happened to be the original
question. I don't think that opening and closing the database in
read-only/recovery mode every five minutes will come close to the SLA
that running the reports needs.
In flight information display systems on airports we used triggers to
achieve the goal Marc is looking for.
We had a bunch of PL/SQL generating views and SQL, that actually created
a complete set of triggers on all tables in a given schema. The triggers
took care of creating entries in a logging table. This table was read
asynchronously by the 'standby database'. This was a system with appr. 2
- 10K transactions per day. Yes, there was quite some overhead, but this
was some 10 years ago, and advanced replication (AR) wasn't there, nor
was Advanced Queueing. So, we built our own AR/AQ solutions, based on
triggers and the dbms_alert package.
These days I would go for AR or Streams, and with 10g, maybe even SQL
Apply/Logical Standby.
So Marc, I think you're stuck: standby (manual/semi-automatic) doesn't
help you. AR is part of EE as well, IIRC. So, it's either generating
triggers and go the cumbersome management way, or going EE. The trigger
thing might very well beat your reporting load, so, maybe running the
reports on the primary and put the standby (manual standby) on the
second server is a better solution. I understand your fear of RAC
complexity completely, however, just to have all options passed your
mind, think of this: RAC with SE on two small servers. OLTP/batches
connect to one instancer, reports to the other (no load balancing and
maybe even no failover config). The standby database (manual apply to
avoid EE licensing) can run on the second server as well. Now you've
off-loaded the OLTP instance from reports, and you have two databases.
You pay per processor, but are free to run two or more instances on the
same server. The recovery process can only hurt the reporting (and vice
versa) but that shouldn't be too bad. I'm sure Mogens will love this
config, as he is director of a small database consultancy company ;-)
Mark is right about the licensing. I've seen customers getting the
standby for 75% off, but you need a license. Only a cold standby, no
Oracle software running, can go for free. As soon as it runs at 10
calendar days or more during a year, be it for failover or testing the
scenario, you need to license that cold server as well.
Best regards,
Carel-Jan Engel
===
If you think education is expensive, try ignorance. (Derek Bok)
===
On Mon, 2004-09-27 at 16:05, Mark W. Farnham wrote:
> Clarification was made that getting individual manual standby strategies
> correct was not generally supported, and support did not cover getting free
> consulting in this regard, but physical recovery was most certainly NOT
> desupported. License issues regarding the recovery machine were not
> generally addressed until much later, probably when standby recovery became
> an official feature with more robust built in support for keeping it
> "right."
>
> I'm not sure who did it "first." I do remember hearing "but you're only
> allowed to do that with support from Oracle Consulting" some number of years
> after I had considered it a routine way to support rapid recovery and the
> creation of databases (cancel recovery, copy, startup with rename open
> resetlogs) as a convenient frozen image for decision support and loading
> time series information into long term data stores (warehouses, marts,
> etc.).
>
> At this writing, though, I believe that Oracle will insist that you must
> license the additional machine. If you don't plan that the machine would
> actually be for fail-over, though, I suppose that the additional license for
> a manual solution could be for quite a modest machine and a small number of
> users. I'm not sure whether the latest specification for the DataGuard
> license requires licensing for the same level as the primary machine (albeit
> with discounts), but a small machine manual standby certainly opens the
> question of possible major savings. Some folks over the years have
> negotiated things such as loading an alternate system for verification of
> the integrity and recoverability of backups, but I think Oracle tends to put
> a "certain number of times per year" limit in new licenses covering that
> issue.
>
> Regards,
>
> mwf
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