Re: DBWR and LGWR processes, theoretical question

Hi 'VBuehringer',

thanks for your response.

vob schrieb:
> so you have found it out, oracle will never work ...

That is not the point. I used Oracle 7 in a complex project and i was very satisfied with it. During the ten years the system is running now at the customers side, we only had one time to deal with trouble in the database due to a hardware failure and we could recover it. Our fortune was that the database was running in redo log archive mode (due to our proper setup :-) ). There were other hardware failures but Oracle ever could recover the database during startup by itself.

> oracle is a technical perfect system and this are the basics
> which you only need to understand that they work perfectly for you
>
> try to learn the new features and use it to its best
>
> few examples :
>
> - replace sqlldr with external tables ..
> - replace rollback segments with undo tablespaces
> - automatic pga management
> ....

I working on it. I've just studied the concept of external tables and i think they are very usefull to solve different flavours of interface problems without having the overhead we had before using tools like SQLLDR. An easier administration for the rollback theme by switching to a reliable new undo concept and for the PGA would be fine. I'm in studying it.

> and don't worry that crash recovery will not work ...because their concept
> is bad this is ridiculous

I don't think that the crash recovery of Oracle will not work. As i mentioned before, this is not the point. What i want to understand is what i need to do to avoid data loss in cases as described in my initial posting. Therefore i need to understand the underlying concepts.

I feel confident that Oracle is much better than most other database management systems if it is not the best one - at most in the really important point of storing the data in a very reliable way.

For example, they _have_ redo log files. Some other database systems even don't have them. In Oracle i can recover my data to a point of time later than i started my last backup. And this feature is implemented since at least 10 years and it does its job as i know from my own experience - this is superb :-)

But, am i on the right side if i use the redo log file duplexing? How many groups do i need (in the past i used two groups for both redo log and control files on different physical datastores)? Do i need to do anything more? What is with the time gap i described in the initial posting? Do i need to care with it? How?

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Michael Gast
SEPP MED GmbH