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Decyphering LMT space bitmap

From: Jeremiah Wilton <jwilton_at_speakeasy.net>
Date: Mon, 08 Apr 2002 11:44:04 -0800
Message-ID: <F001.0043ED56.20020408114404@fatcity.com>


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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Author: Jeremiah Wilton
  INET: jwilton_at_speakeasy.net

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