Re: Bitmap header and footer sizes

Notwithstandin Oracle notes to the contrary, I am not convinced that (in 8.1.5 at least) there is such a thing as a bitmap footer.

Also, I have not yet managed to create a datafile larger enough to require more than 64K of total file header (i.e. header block(s) + bitmap blocks) although I don't have a platform that will support the 32K Oracle block size, so my tests are incomplete.

Depending on block size, a 64K header maps 27,000 to 30,000 uniform extents, so your 1Gb file will have no trouble with your 250 4MB extents.

If you want precision, you could create your raw at

    1 Oracle block (platform dependent) +     64K +
    N x extent size.

If you want safety, just build a file which is a of megabytes larger than the total extent space you want to allocate. You waste the best part of a megabyte - but that's a small price to pay for peace of mind.

--
Jonathan Lewis
Yet another Oracle-related web site:  http://www.jlcomp.demon.co.uk

Practical Oracle 8i:  Building Efficient Databases

Publishers:  Addison-Wesley
See a first review at:
http://www.ixora.com.au/resources/index.htm#practical_8i
More reviews at: http://www.jlcomp.demon.co.uk/book_rev.html



Frank Black wrote in message ...


>Hi all,

>

>how do I calculate the size of the header and footer bitmaps of locally

>(uniform) managed tablespace datafiles?. I need to know it for sizing

>datafiles (chunks) on a RAW device.

>I want to create uniform tablespaces with for example a 1Gb datafile with

>4Mb uniform extents, Oracle block is 8Kb;

>

>1024*1000/4096 = 250 (extents in one datafile).

>

>For the headerfile I need 1 block, using RAW devices also one block needs

 to


>be added which makes:

>1024000Kb + 8Kb + 8Kb + headerbitmap (Kb) + footerbitmap (Kb) = size of RAW

>device chunk. (Am I right?)

>

>But how to calculate the size of these bitmaps?

>

>thanks in advance,

>

>Hink Wiersema

>

>