Re: Extent sizes

"PK" <pk26au_at_yahoo.com> wrote in message news:1127700032.457698.161630_at_g47g2000cwa.googlegroups.com...
> Jonathan,
> That explains it very well.
> The level 1 bitmap that covers the present and the next extents - is it
> normal for all locally managed tablespaces ?
>
> Thanks again,
> PK
>

There are some minor variations in behaviour dependent on extent sizes and segment sizes. For example, I have a tablespace with 1MB uniform extents, and ASSM. The first extent has

    2 x level 1 bitmap blocks
    1 x level 2 bitmap blocks
    Segment header block

The second extent has

    2 x level 1 bitmap blocks

Each level 1 bitmap covers 64 blocks
of the extent it's in.

I think that when the segment gets to
1GB, the blocks in my example will fall
back to one bitmap block per extent (but I haven't tested that since the very early releases - so it may have changed).

You may find (pure conjecture here) that at a certain size, your system could switch to:

    1 bitmap block per extent
    4 bitmap blocks every 4th extent covering 4 extents

And there's always the possibility that the actual behaviour depends on how many other extents from other segments end up falling between the extents of the one segment you are experimenting with.

-- 
Regards

Jonathan Lewis

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