RE: Auto Extend

Hi John,

I still haven't learned not to make sweeping statements on mailing lists = ) I expected someone to raise SMON or checkpoint overheads so I added "necessarily" very deliberately.

Agreed, I'd tend to keep the number of files down to a reasonable number but I've run a database with 3,500 datafiles and it didn't choke on log switches at all. As you say, appropriately sized redo logs can mitigate the effects to some extent.

Regards,
Mike Hately,
Oracle DBA

John Kanagaraj <john.kanagaraj_at_hds.com>

>Neither large files nor small files are evil. As with all
>things, fit the
>solution to the problem.
>Small files can leave you with lots of separate datafiles which isn't
>necessarily a drag on performance but can be an administrative
>chore and can
>cause more wasted space due to that pesky 'end-of-datafile'
>free extent.

Mike, I will have to disagree with you about small files not necessarily being a drag on performance. Given a specific size of a database, it would be better to go in for larger files (avoiding the >2Gb pitfall if possible) since each datafile adds its own component to the flurry of I/O activity that takes place during log switch, i.e. when all datafile headers need to be updated.

In simpler terms, (Large number of) Small datafiles + small redo logs + high DML activity = disaster during (the frequent) log switches...

>People who want to
>set up databases larger than a terabyte will inevitably have a
>budget to invest
>in new kit and buy-in to up to date OS and software levels.
>Not everyone has
>that luxury and a lot of legacy kit doesn't like 2GB+ files.
>
>That's only my opinion but really, why play around with any
>area that is
>demonstrably strewn with bugs unless you need to?

Fully agreed!

John Kanagaraj

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