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Oracle 10g and database corruption with hard shutdown

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Coolmar
Esteemed Contributor

Oracle 10g and database corruption with hard shutdown

Hi,

I have a question regarding Oracle 10g. Back in the day, if Oracle was not shutdown properly before powering off a server, you ran a good chance of database corruption. I was wondering if that is still the case for 10g. THe reason I am asking is that we recently had a power-outtage. When the UPS got low, I shutdown the databases and servers properly. A collegue feels that we should just let them run until the power just shuts off and therefore bringing the systems and database down hard. He feels that Oracle is mature enough at 10g that there will not be any corruption. Any thoughts?

Thanks,
SD
11 REPLIES
Pete Randall
Outstanding Contributor
Solution

Re: Oracle 10g and database corruption with hard shutdown

Most UPS systems have some provision to interface with the machine they power so that normal shutdown procedures can be invoked when power is nearly exhausted. There's a good reason for that. I would always prefer to gracefully shutdown.


Pete

Pete
HugoAlmeida
Trusted Contributor

Re: Oracle 10g and database corruption with hard shutdown

I have worked with Oracle 8i and 9i. The only time i have got a problem with hard shutdown was caused by a faulty design of the database model and not of the Oracle database. However, i think is always best to shutdown the database because if the power goes down hard you will always loose some kind of information that was in the RAM or in the aplications servers. Hard shutdown will always stress the hardware, and there is a real chance of hardware failure resulting of a hard shutdown.

Just some thougths.
Patrick Wallek
Honored Contributor

Re: Oracle 10g and database corruption with hard shutdown

Well, if that is your colleagues opinion, tell him he can be the one to recover it if the DB is hosed.

I would most definitely NOT want to just pull power on a machine. If you have the time, and it is possible, I would VERY HIGHLY RECOMMEND shutting the database down clean first.

If you just pull the plug, there is a risk of corruption especially if someone was in the middle of something when the system goes down.
Jean-Luc Oudart
Honored Contributor

Re: Oracle 10g and database corruption with hard shutdown

Sally,

Oracle can recover by itself.
When you start the instance Oracle will roll back uncommitted transactions and roll forward the committed one. If you run a shutdown abort and then re-start the database check the alert log file for these messages.
Saying that if you know your server is to be brought down you should bring them down in a clean way.

Regards
Jean-Luc
fiat lux
A. Clay Stephenson
Acclaimed Contributor

Re: Oracle 10g and database corruption with hard shutdown

Oracle from about 7.3 onward has been rather good at automatic recovery ("rather good" <> "perfect"); however, it is state of the art stupid not to do an orderly shutdown when given the chance. Have your colleague consider the case of a UNIX write() using cooked files. As far as the application knows the write() has been completed but in reality the only thing that may have completed was the write to buffer cache. The exact behavior under this scenario depends upon a number of factors (type of filesystem, mount options, open() options, and most importantly, timing) but in any event there are paths which can lead to corruption.
If it ain't broke, I can fix that.
Florian Heigl (new acc)
Honored Contributor

Re: Oracle 10g and database corruption with hard shutdown

In short, I'd recommend him to look into a different occupation.

In long, he's right in almost any case, with exception to for example a delaylog-mounted filesystem on a disk with immediate_report=1 in combination with san connectivity loss [think HP-UX+FC-AL+FC4500 and add tresspassing] leading to hang of the sdisk driver, leaving to lost unflushed data.

These things *can* and *do* happen, and it's never, ever wise to risk data. someone is paying him for keeping the data safe, and he recommends the very opposite.
yesterday I stood at the edge. Today I'm one step ahead.
Steven E. Protter
Exalted Contributor

Re: Oracle 10g and database corruption with hard shutdown

My Oracle experience is the database CAN and usualy does recovery from sudden power off.

But its our jobs as sysadmin's to make sure it NEVER happens.

SEP
Steven E Protter
Owner of ISN Corporation
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TwoProc
Honored Contributor

Re: Oracle 10g and database corruption with hard shutdown

Geez,

Sure Oracle can usually recover by itself, but do you really want to pur yourself and your company through all that hassle the ONE TIME that it didn't? Especially when you've got time to shutdown first? The costs of failure are way too high (for you and your company) when the cost to avoid is so small, even when the risk is low.
We are the people our parents warned us about --Jimmy Buffett
Yogeeraj_1
Honored Contributor

Re: Oracle 10g and database corruption with hard shutdown

hi Sally,

I agree with john above, for sure Oracle will do automatic recovery BUT is your organisation ready to take the risk of any data corruption possibility (1 in a million maybe)? I sincerely believe that you should be able to provide a more scientific solution to your organisation.

I would never go for an easy solution with High risks! ( for sure Oracle would not recommend what your collegue "feels" ok)

Don't go for Hearsays! look for documentary proofs (if any)

good luck!

kind regards
yogeeraj


No person was ever honoured for what he received. Honour has been the reward for what he gave (clavin coolidge)
Arunvijai_4
Honored Contributor

Re: Oracle 10g and database corruption with hard shutdown

Oracle 10g has got self recovery in-built.
http://www.oracle.com/technology/products/manageability/database/pdf/twp03/TWP_manage_self_managing_database.pdf

-Arun
"A ship in the harbor is safe, but that is not what ships are built for"
Coolmar
Esteemed Contributor

Re: Oracle 10g and database corruption with hard shutdown

Thanks!