Oracle-L: Re: Decyphering LMT space bitmap

From: Danisment Gazi Unal <dunal_at_unal-bilisim.com>
Date: Mon, 08 Apr 2002 13:33:25 -0800
Message-ID: <F001.0043EFC9.20020408133325@fatcity.com>

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
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Jeremiah Wilton
> INET: jwilton_at_speakeasy.net
>
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--
Danisment Gazi Unal
http://www.unal-bilisim.com



-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Danisment Gazi Unal
  INET: dunal_at_unal-bilisim.com

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Received on Mon Apr 08 2002 - 16:33:25 CDT