Re: type of striping

From: Howard J. Rogers <hjr_at_dizwell.com>
Date: Wed, 08 Dec 2004 10:48:57 +1100
Message-ID: <41b64168$0$12876$afc38c87@news.optusnet.com.au>

Fabrizio wrote:
> Howard J. Rogers wrote:
>

>>
>> Autoallocate is probably my preferred way of creating LMTs.
>>

>
> From your old posts I always thought you preferred the "uniform size"
> for LMTs.
>
> May I ask you the advantages of autoallocate?
>

Ah... I just answered you via email, because that showed up before this post. Could I ask you not to email me things you are also going to post to the newsgroup? That way, I don't get confused! (Happy to have email for other stuff, of course). Anyway...

It's true I was always a little suspicious of autoallocate, because it was very difficult to pin down precisely what extent sizes you were going to get. I hesitate to recommend anything I don't really understand.

But that changed a long time ago. I now believe that DBAs really shouldn't have to worry about extent sizing at all, and autoallocate takes that chore away completely. PCTINCREASE used to do something similar, of course, with the same sort of 'automation' claims, but the consequence was horrendous fragmentation issues... autoallocates don't fragment (or exceedingly rarely, anyway).

> May I ask you the advantages of autoallocate? >

Total automation for one.

For another, ASSM is in widespread use, and that makes the number of extents an issue again. Autoallocate minimises the number of extents. Poorly chosen uniform sizes will cause grief with ASSM.

Besides which... look at what 10g is doing with ASM, and you'll see that the days of ever worrying about extents are (or should be) long, long ago.

But I'm not religious about it. If you want to steer clear of autoallocates (perhaps because of the no striping issue discussed earlier, and your particular hardware) that's fine, too.

Regards
HJR Received on Tue Dec 07 2004 - 17:48:57 CST