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Database Forum / DB2 Topics / July 2006Tablespace - mysteriously lost pages.
Hello, all. Let the tablespace SY810T4K is almost full: --------------- db2 => list tablespaces show detail ... Name = SY810T4K Type = Database managed space Contents = Any data Total pages = 332800 Useable pages = 332736 Used pages = 268480 --------------- I thoroughly checked that only tables' data (no indexes or LOBs) lie in this tablespace, run statistics for each table in tablespace and computed: Allocated pages: "sum( fpages ) from syscat.tables" == 256679 (for tables in tablespace SY810T4K) Surprisingly, this number is not equal to "Used pages" number returned by "list tablespaces" command. Who may use the rest of the uses pages in tablespace ? "Used pages" - "Allocated pages" = 268480 - 256679 = 11801 LOST (?) pages. Thank you in advance, -- Konstantin Andreev. They are not LOST. When was the last time u ran REORG on the tables in this tablespace ? U might need to re-claim the space using REORG cheers... Shashi Mannepalli > Hello, all. > [quoted text clipped - 23 lines] > -- > Konstantin Andreev. > They are not LOST. When was the last time u ran REORG on the tables in this tablespace ? Never, yesterday, a month ago... it does not matter. You are looking in wrong place. > U might need to re-claim the space using REORG REORG <table> reclaims pages excessively allocated for this <table> (fpages - npages). REORG has nothing to do with pages, used in tablespace, but *NOT* allocated by any table. For sure, I have run REORG and RUNSTAT for each table in tablespace, but got just another number of LOST pages: --------------- db2 => list tablespaces show detail ... Tablespace ID = 22 Used pages = 268480 --------------- db2 => select sum(fpages) from syscat.tables where tbspaceid=22 1 ----------- 270105 LOST: (270105 - 268480) = 11847 pages. Cheers, Konstantin Andreev. >> Let the tablespace SY810T4K is almost full: >> --------------- [quoted text clipped - 17 lines] >> >> "Used pages" - "Allocated pages" = 268480 - 256679 = 11801 LOST (?) pages. > Hello, all. > [quoted text clipped - 26 lines] > -- > Konstantin Andreev. The ANSI Standards Board has set those pages to NULL and you will never see them again. DMS managed tablespaces require overhead of one extent per container. Also, free pages aren't freed up unless you do an offline reorg. You should see them as pending free on a tablespace snapshot...PG > Hello, all. > [quoted text clipped - 23 lines] > -- > Konstantin Andreev. > DMS managed tablespaces require overhead of one extent per container. Its actually more than that. The one extent/container you quote is for the container tag only - this is reflected in the disparity between 'total pages' and 'usable pages'. There is additional overhead associated with the tablespace's metadata - both per-tablespace (ie, the SMP extents) and per-object within the tablespace (ie, the EMP extents for each object). jsoh Check this technote http://www-1.ibm.com/support/docview.wss?rs=71&context=SSEPGG&dc=DB520&q1=LOB&ui d=swg21197191&loc=en_US&cs=utf-8&lang=en cheers... Shashi Mannepalli > > DMS managed tablespaces require overhead of one extent per container. > [quoted text clipped - 7 lines] > > jsoh |
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