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Home -> Community -> Usenet -> c.d.o.server -> Re: One vs many databases
There's a limit where "many" is "too much". But if we're talking about a
handful of systems, it may make sense to house them in separate
databases. There's no simple answer. The way the original question was
posted, I don't think any of us know enough about John's systems to use
"never" or "always" in our replies.
If the applications are different in their resource requirements, a good way to protect one application from the other's work cycle is to separate them. Otherwise you'll spend the rest of your life apologizing for payroll running slow whenever your accounting dept is reporting on the general ledger.
You can tune some databases for OLTP (say, help desk, PO) and others for batch (payroll, accounting).
Furthermore, if you have a corrupted SYSTEM tablespace, only one of your databases needs recovery. It's the difference between any DBA task affecting 10% of the company versus affecting the whole company.
Sometimes I find it much easier to manage a few databases than just one (again, there's a number where "a few" is "too much"). Because if you have all your systems in one database, a single bad-performing query can generate two dozen phone calls. To your extension.
In a way, DBAs also have to manage people's fears and expectations. The best DBAs I know take the time to keep their users (the real owners of the databases) appraised of all problems, issues and trends. And this is a much easier thing to do if you don't have to broadcast every single problem to the whole company.
shridned wrote:
> I never understood why somebody sensible with technical know how,
> would like many databases instead of one.
>
> I have seen a billing system of a big telecom company
> they made a seperate database for every big table, call the crap
> "distributed databases, this is cool" and it is very good,
> very good in employing 100 dba and up to now produced 1 billion euro cost.
>
> so the answer to this is "someone sensible and knowledgeable " would
> never prefer many databases instead of one.
>
> the only reason for many databases the usage of standard software which
> forces you to seperate your databases and use different oracle versions.
>
> but with home made software the best this is to integrate everything into
> one big
> db with 9.2 and make some standby databases on different places to
> protect it
>
> sometimes people tell you, if the thing is to big it is difficult to manage.
> but this people have no real oracle knowledge , at how much more difficult
> is
> it to manage seperate databases instead of one.
>
> for the problems with big data volumes we have today big hardware and I used
> a technique to seperate the historical data through partitioning into a
> seperate
> partition and used the compress option in 9.2 and sorted it to "compress"
> it.
> but logical it stays in the same table and everything is simple
>
> people told me the historical data needs to be in a seperate database
> to keep the working database "fast" but this is also nonsense. If you need
> the data keep it in the primary database and organize it well, as I did.
> I you don't need it remove it.
>
> Ask this question Thomas Kyte from Oracle and he will tell you the same.
> He is one of the few Oracle authorities from which you really can learn,
> most people in this area have no real knowledge from modern
> system management. they only want to keep their job and make it as
> difficult as possible, like this people telling you to reorganize database,
> indexes ...
>
> Also if it is really necessary you can use RAC to use many servers for one
> big database, it is still much more simpler than many databases because
> logical you have only one, but only if you really need it.
>
>
>
>
> "John Hunter" <jthunter_at_nbnet.nospam.nb.ca> schrieb im Newsbeitrag
> news:qufR9.3254$Hs3.402088_at_ursa-nb00s0.nbnet.nb.ca...
>
>>Hi Gang, >> >>I'm looking at submitting a business case to management that will justify >>changing from our current structure of many oracle databases to one big >>database. We currently run many separate databases (financial, sales, >>purchases etc...) all based on functional areas. These are all inhouse >>written systems. My problem with having all these instances is with
>>to link data together. We need to have realtime data shared amonst the >>systems. Dblinks are quite slow and although materialized views have lots >>to offer they consume a fair amount of overhead. >> >>Anyway, I've done some web searches looking for the pros and cons of many >>instances vs. one instance and have yet to find a good whitepaper on this >>subject. I did read through the long (70 or so posts) when someone said
>>were going to install 50 instances on one host, but it didn't really
>>the question. >> >>Thanks, >>-John >> >> >> >>
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