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Bitmaps and Freelists [message #255032]

Mon, 30 July 2007 08:05

naveenkumar001
Messages: 62
Registered: July 2007
Location: Bangalore

Member

Hi,
Can anyone help me in this matter:-

When i was studying locally managed tablespaces i came across bitmaps that are used in locally managed tablespaces it stated that:-
"Locally managed tablespaces use bitmaps stored within the header of the datafiles comprising a tablespace to track the space utilization of the tablespaces."

AND

When i was studying some other topics i came across FreeLists it stated that:-
"Oracle will first search for a free block in the FREELIST and then the data is inserted into that block. The availability of the block in the FREELIST is decided by the PCTFREE value. Initially an empty block will be listed in the FREELIST structure, and it will continue to remain there until the free space reaches the PCTFREE value"

Q) I am confused of Bitmaps and Freelists as they have been used for same purpose whether Bitmaps means Freelists only or is there any difference between them ?

Regards,
Naveen

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Re: Bitmaps and Freelists [message #255038 is a reply to message #255032]

Mon, 30 July 2007 08:24

Michel Cadot
Messages: 68737
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

Quote:

Q) I am confused of Bitmaps and Freelists as they have been used for same purpose whether Bitmaps means Freelists only or is there any difference between them ?

No there are 2 different things and there are no relation between them.
Bitmaps (these ones) manage blocks/extents in a tablespace.
Free lists manage blocks inside a segment.

Regards
Michel

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