Re: Dbspace Question.

Abhay Mannur wrote: > > Hi, > I'm sure of the 6 dbspaces assigned to a perticular database. > Also I'm sure that no other tables from any other databases are residing > there. > When I drop that database and look at the chunks, I get the following > output. [onstat -d output SNIPPED] > I'm curious about the free pages in each chunk. > Most of them show 3 used pages. > Some of them has different number of used pages. > > Why is this ? The amount of free space contained in a chunk when it is empty depends on several factors. Those chunks showing only 3 pages used either have never been used or are not the first chunk in the dbspace and contain no overflow tablespace tablespace pages. Each chunk's first two pages (pages 0 & 1) are unused and generally contain garbage but are counted as used since they are never used. Page 2 is the chunk's ID page and contains a page header identifying it as page 2 of chunk N and little else. Hence the 3 used pages of any otherwise empty chunk. OK so the chunks with more used space? The first chunk of a dbspace has additional overhead pages including an initial tablespace tablespace page and bitmap page. In addition if any tables or fragments were created in the dbspace there will be pages used for each table's tablespace tablespace entry which, while cleared, is not freed when the table is dropped. If the first chunk of the dbspace is full and the tablespace tablespace needs to be expanded to make room for some new table's entry the tablespace tablespace will allocate a new extent in another chunk which may explain why some none-first chunks have larger minimum allocations. Hope that helps your understanding. This is off the top of my head, but if you read carefully you can glean all of this and the details from the Administrator's Guide. > I want to drop these dbspaces. So before doing that, I want to know > about 'em. Art S. Kagel