From: Greg Parsons <parsons@intermetrics.com>
Subject: Re: Layout of a database block
Date: 1998/02/02
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Hi Arnold,
	Try Server Concepts Manual.  For Oracle 7, it's chapter 3.  
	Usually a multiple of the O/S block size, made of 5 components to a
(partially filled) block, header, table directory, row directory, row
data and free space.  This is the short course...
	The Pctfree and Pctused parms let you manipulate how the block will
control it's free space and when the block will consider itself full and
chain on further inserts.  
	The header contains the block address and type of segment (data, index
or rollback).
	The table dir tells Oracle which tables store data here.
	The row dir addresses each row data in the block.  Row deletion does
not release this space back to the free portion of the block.
	The row data and free space are controlled by the parms listed above. 
Upon deletion of row, releases space back as free.
	Hope this helps.

Greg


Arnold Wentholt wrote:
> 
> Hi,
> 
> I'm curious about the exact layout of an Oracle database block.
> 
> A block can contain contains rows, transaction entries, checksums, but what
> exactly is in a block? I hope an explanation of the contents of a database
> block will give me a better idea of the architecture of the Oracle server.
> 
> Any documents about this issue?
> 
> Thanks,
> Arnold Wentholt