Block Dump Interpretation

From: mohammed bhatti <mkb125_at_yahoo.com>
Date: Tue, 25 Sep 2001 11:12:19 -0700
Message-ID: <F001.0039830F.20010925104034@fatcity.com>

OK, so somebody asks me if there is a way to determine how full an Oracle data block is. I've been playing around with dbms_space and dbms_rowid packages but apparently, I can't see how these would help. A couple interesting scripts both on ixora and Jonathan Lewis web site seem to have helped. I used JL's script 'alter system dump datafile <df_no> block min <min_blk> block max <max_blk>;' to dump the segment header and block headers for various data blocks.

For example, if I run this:

alter system dump datafile 122 block min 4 block max 4, I dump the header info for block 4 in datafile 122.

Question is, when I look in the trace file I see the following line:
block_row_dump
tab 0, row 53, @0x46c
tl: 2 fb: --HDFL-- lb:0x1
...
...
tab 0, row 98, @0x1f21
tl: 2 fb: --HDFL-- lb: 0x1
end_of_block_dump

So, am I correct in assuming that there are 46 rows
(98-53+1=46) in this block? If this is the case, I
would be able to calculate the average row size for this block and do all sorts of silly little 'rithmetic calculations based on pctfree etc. This would give fairly granular insight into how tightly packed blocks are, right?

Any opinions?

tia

mkb

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Author: mohammed bhatti
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Received on Tue Sep 25 2001 - 13:12:19 CDT