Re: Decyphering LMT space bitmap

That looks the way it should be.

You have 30 extents in the tablespace, and 30 bits near the start of the bitmap are set.

You'll have to create a bitmap tablespace and use extents in it one at a time, but quite literally from the block 3 onwards the bitmap is one bit per extent - it's just a question of working out the byte and word swapping in the dump.

Temporary tablespaces are different, though, as the 'bitmap' is actually 2 bytes per extent because temporary extents 'belong' to instances and each 'bit' needs to have the current owning instance associated with it.

Jonathan Lewis
http://www.jlcomp.demon.co.uk

Host to The Co-Operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html

Author of:
Practical Oracle 8i: Building Efficient Databases

-----Original Message-----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: 08 April 2002 20:08

|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
|
|

-- 
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-- 
Author: Jonathan Lewis
  INET: jonathan_at_jlcomp.demon.co.uk

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