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[#] Wed Mar 31 2010 12:32:33 EDT from LoanShark @ Uncensored

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Mar 31 2010 10:46am from Peter Pulse @uncnsrd
I see it from a different point of view.. if I am going to pay a
kazillion dollars for a database and people to run it, it damn well
better have referential integrity. That is one of the MAJOR selling
points of these systems isn't it???



Ok, well yes and no. It's a major selling point of RDBMS in general I agree with that. I don't agree that it's a major selling point of Oracle in specific, because it's become a very commoditized feature let's face it. Most of the major open source RDBMSs implement it... the value proposition of Oracle is further up the pyramid, with things like partitioning, and RAC, and replication, and all those fancypants SQL extensions, like analytical queries (some of which are standard ANSI SQL now, btw.)

In any case, foreign keys sometimes just don't work, because they can impose unpredictible lock orderings on your queries. Every time you issue DML on a constrained table, Oracle (and probably every other RDBMS suffers the same problem) spawns a child cursor/query against the parent/child tables to check indexes and enforce constraints. That child query creates the lock-order problem and as near as I've ever been able to tell, the ordering is simply undefined and can't be relied on.

So most likely FK constraints will work just fine for you for months or years, but eventually as your load creeps up and your schema becomes more complex and you have more and more disparate queries hitting it, you will start running into ORA-00060 (deadlock.) And most likely the problem is universal across RDBMS.

When this does happen, you can spend a lot of time scratching your head, analyzing Oracle dumps, and trying to fix your queries to consistify the locking order. But you will likely fail - so you either have to code around the ORA-00060 with retries, or just drop your constraints. Best not to go down the analysis route - it's so unlikely to work - just retry queries or drop constraints.

This is one reason you should never write code that DEPENDS on the presence on FK constraints in some what, particularly code that relies on CASCADE DELETE. Code must continue to function properly if the constraints have to be dropped, some day.

[#] Wed Mar 31 2010 12:32:42 EDT from LoanShark @ Uncensored

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some what = some way

[#] Wed Mar 31 2010 15:58:00 EDT from Ford II @ Uncensored

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Ahhh cascade delete how I miss thee.
Speaking of our genius DBA, I was somewhat surprised that sybase didn't have cascade delete, and because of some reason I forget I wanted to delete stuff in the cascade delete order, but the foreign key constraints the DBAs put on my tables didn't allow for that.
So my sprightly (spritely?) dba told me he'd write a trigger to implement cascade delete
.
Scratching my head I wondered how this was going to work without removing the fk constraints. After much banging his head, he let it drop, as in gave up, and I still have to delete my stuff backwards.

Shouldn't be that hard. But it is, it always is.

[#] Wed Mar 31 2010 16:01:18 EDT from Ford II @ Uncensored

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But that's not what I wanted to talk about.
I recently reached a milestone in my life. Since I was about 23 or so I've never run less than 2 machines, one for my use and one fo the websites I run and mail and whatever else. Well finally I consolidated, and I have everything on one big ass machine.
There are many downsides, but this is the way it's going to be for a while, and I think my most pressing problem is that I have no online machine to back this machine up to.
I used to rsync back and forth between the two. Now there's nowhere to rsync to.
This machine has raid0 via linux so it's not completely at risk, but I'd still like somewhere else to go.
so I was thinking the memorystick angle. I see you can buy a 64gig stick on ebay for about $20-$30. Is this reasonable or is this crap from china that will write once read never?

Or does anybody have a better idea? I've got about 36gig to back up at the moment.
Sad my whole online life fits in 36gig.

[#] Wed Mar 31 2010 16:01:53 EDT from LoanShark @ Uncensored

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That trigger might actually work on Oracle because of the deferred constraints feature.

[#] Wed Mar 31 2010 16:03:28 EDT from LoanShark @ Uncensored

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I bought a 1TB external disc for backup, but Steve Ballmer probably made me do that.

[#] Fri Apr 02 2010 02:35:22 EDT from the8088er @ Uncensored

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Okay, I just learned about the robocopy command that was added as a standard tool in Vista. It is an awesome copy tool.

Check it out if you use Windows and haven't seen it.

[#] Fri Apr 02 2010 08:35:01 EDT from fleeb @ Uncensored

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That is kind of interesting. It might come in handy, if I can ever get away from XP.

[#] Fri Apr 02 2010 12:48:56 EDT from wizard of aahz @ Uncensored

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From what I'm hearing using RoboCopy took one of our backup processes from 15 minutes to 4 minutes.. Not sure of the details yet though.

[#] Fri Apr 02 2010 16:09:38 EDT from fleeb @ Uncensored

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I wonder if it's kind of like an rsync.

[#] Fri Apr 02 2010 16:13:08 EDT from the8088er @ Uncensored

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It allows you to only copy changed files or files that don't already exist which is extremely convenient.

[#] Fri Apr 02 2010 16:14:15 EDT from Peter Pulse @ Uncensored

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Thanks to ig I started using rsync regularly, I back up the home directory of my work desktop (actually a laptop running Ubuntu) to a server every night.

[#] Sat Apr 03 2010 01:27:50 EDT from IGnatius T Foobar @ Uncensored

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I've seen robocopy run, and I've seen rsync run. rsync *smokes* robocopy in terms of performance.

[#] Sat Apr 03 2010 03:36:15 EDT from the8088er @ Uncensored

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Well, by default robocopy retries one million times on failure and waits 30 seconds between retry. That could have something to do with it.

Even so, out of the box robocopy is the only way on Windows to copy files without bothering to rewrite existing ones -- Very useful for large interrupted file transfers.

[#] Sat Apr 03 2010 06:01:42 EDT from fleeb @ Uncensored

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It probably doesn't send binary differences, as rsync does.



[#] Sat Apr 03 2010 11:39:21 EDT from IGnatius T Foobar @ Uncensored

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It probably has something to do with the fact that Windows tends to get cranky when you try to backup open files.

[#] Sun Apr 04 2010 11:58:54 EDT from Ford II @ Uncensored

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There's the problem of having the other server to backup to.

[#] Tue Apr 06 2010 17:36:29 EDT from dothebart @ Uncensored

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so the legacy found anotherway:

http://en.wikipedia.org/wiki/Dolby_Laboratories#Audio_processing

dolby mobile so its not just tapes and home cinema stuff...



[#] Thu Apr 08 2010 13:18:54 EDT from IGnatius T Foobar @ Uncensored

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Absolutely. Dolby Pro Logic II is *the* standard way to encode surround sound into formats that only supply two channels.

I hear it every day when my kids turn on the Nintendo Wii. :)

[#] Thu Apr 08 2010 14:51:18 EDT from dothebart @ Uncensored

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well one of its shortcommings: no digital audio out...else it would be a perfect dvd player. (hacked and with mplayer)



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