Jeremiah,

Let me explain before guru X$GOPAL woke up. I guess time is midnight in India.

Here are the some lines before your dump:

Start dump data blocks tsn: 1 file#: 2 minblk 3 maxblk 3
frmt: 0x02 chkval: 0x0000 type: 0x1e=KTFB Bitmapped File Space Bitmap
File Space Bitmap Block:
BitMap Control:
RelFno: 2, BeginBlock: 5, Flag: 0, First: 30, Free: 128994
FFFFFF3F00000000 0000000000000000 0000000000000000 0000000000000000
0000000000000000 0000000000000000 0000000000000000 0000000000000000
0000000000000000 0000000000000000 0000000000000000 0000000000000000
... all zeros

Let's convert your HEX bitmap vectors to binary. It's 0xFFFFFF3F in your case.
In other words, it consists of 4 bytes. They are 0xFF, 0xFF, 0xFF, 0x3F.
The binary equivalents: 1111 1111, 1111 1111, 1111 1111, 0011 1111.

To read this bitmap, we should take the least significant bit the first for each byte pair:
The new bitmap will become: 1111 1111, 1111 1111, 1111 1111, 1111 1100

Now,

Each '1' represents used extent, each '0' represents free extent. If We look at the position of first '0',
you will see that it's 31th position. Note that this is one more than the First value in the dump given above.
Because Oracle starts looking for free space from the First value in the dump.

You had found 30 extents in dba_extents. Now, we saw it in the block dump too. There is no problem.

btw,

I had a free product named iOraDumpReader at http://www.unal-bilisim.com/products/ioradumpreader/ioradumpreader.html .
It interepretes almost all block dumps. But, since there is no enough hit to this page, I'm not currently working on it.

regards...

Jeremiah Wilton wrote:

Out of curiosity I decided I wanted to look at what composed the
extent map in locally-managed tablespaces.

I dumped the first 5 blocks of the tablespace's first datafile with
'alter system dump datafile ...'  The results surprised me, as they
appeared to consist of almost no data.  The LMT in question contains a
variety of segments and extents.  How is the LMT bitmap organized?

Start dump data blocks tsn: 1 file#: 2 minblk 1 maxblk 1
Block 1 (file header) not dumped: use dump file header command

Start dump data blocks tsn: 1 file#: 2 minblk 2 maxblk 2
frmt: 0x02 chkval: 0x0000 type: 0x1d=KTFB Bitmapped File Space Header
File Space Header Block:
Header Control:
RelFno: 2, Unit: 8192, Size: 524352, Flag: 1
Initial Area: 3, Tail: 524292, First: 30, Free: 34

Start dump data blocks tsn: 1 file#: 2 minblk 3 maxblk 3
frmt: 0x02 chkval: 0x0000 type: 0x1e=KTFB Bitmapped File Space Bitmap
File Space Bitmap Block:
BitMap Control:
RelFno: 2, BeginBlock: 5, Flag: 0, First: 30, Free: 128994
FFFFFF3F00000000 0000000000000000 0000000000000000 0000000000000000
0000000000000000 0000000000000000 0000000000000000 0000000000000000
0000000000000000 0000000000000000 0000000000000000 0000000000000000
... all zeros

Start dump data blocks tsn: 1 file#: 2 minblk 4 maxblk 4
frmt: 0x02 chkval: 0x0000 type: 0x1e=KTFB Bitmapped File Space Bitmap
File Space Bitmap Block:
BitMap Control:
RelFno: 2, BeginBlock: 1056964613, Flag: 0, First: 0, Free: 129024
0000000000000000 0000000000000000 0000000000000000 0000000000000000
0000000000000000 0000000000000000 0000000000000000 0000000000000000
0000000000000000 0000000000000000 0000000000000000 0000000000000000
... all zeros

FWIW:

SQL> select count (*) from dba_extents where file_id = 2;

  COUNT(*)
----------
        30

SQL> select extent_management from dba_data_files df, dba_tablespaces
ts where df.tablespace_name = ts.tablespace_name and file_id = 2;

EXTENT_MAN
----------
LOCAL

--
Jeremiah Wilton
http://www.speakeasy.net/~jwilton

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