Re: How to "Defragment" Tablespaces ?

From: Nuno Souto <nsouto_at_nsw.bigpond.net.au.nospam>
Date: Mon, 09 Apr 2001 15:18:24 GMT
Message-ID: <3ad1d0c5.1274374@news-server>

On Mon, 9 Apr 2001 09:48:29 -0400, Liz Reen <lizr_at_geologist.com> wrote:

>
>A tablespace is much like a disk drive. Think of tables as files. Like
>files tables have extents all through the tablespace. There has to be a
>diskmap sort of data structure which keeps track of the extents and
>tables. This is where the contention happens. I had heard that there
>was a limit of approximately 25 concurrent accesses allowed to this area
>in 7.x. I do not know about 8.x.

Minor correction. With DB2 and other databases, there is a tendency to consider a tablespace as a "file". That is not the case with Oracle. You can have a heap of files making up a tablespace.

But your point about "there has to be a diskmap ..." is quite correct and indeed there can be contention for the equivalent in Oracle. And even with EMCs, it will make a difference. In fact, it is my experience that it is *precisely* with EMCs that you notice this the most, but unfortunately I haven't yet had a chance of proving it beyond any doubt.

Cheers
Nuno Souto
nsouto_at_bigpond.net.au.nospam
http://www.users.bigpond.net.au/the_Den/index.html Received on Mon Apr 09 2001 - 10:18:24 CDT