Tempdb--Allocation Bottleneck
6027 단어 location
PFS(Page Free Space): used to track the followint information about each page:
1. free space available
2. if it is allocated or not
3. has ghost records(when a row is deleted, it is marked as ghost)
PFS use 1byte/page and each PFS page stores stats for 8088 pages
GAM(Global allocation Map): used to trackis a uniform extent is free or not, use one bit to ideitify one extent, so each GAM page stores status for 64000 extents or 4 GB
SGAM(Share Allocation Map): tracks if an extent is mixed extent or not, one bit '1' indicates that it is a mixed extent and has one or more free pages, each SGAM page cover 64000 extent or 4GB
if one objects use more then 7 pages, SQL SERVER will allocate uniform extents for it.
Each database file have thire owm PFS/GAM/SGAM pages.
When one object was created(destoryed) or page was allocated(deallocated), SQL Server need search the allcation page with SH latch and update the allocation page with X latch, multiple thread need to wait to acquire X or SH latch in non coflicting mode which can lead to allocation bootleneck.
starting with sql server 2005, the cahcing mechanism for objects in TempDB Has been improved siginificantly which reduce the alloctaion contention incurred by your workload.
할당 페이지가 막혔는지 확인
--=============================================
-- Tempdb
--http://www.sqlsoldier.com/wp/sqlserver/breakingdowntempdbcontentionpart2
With Tasks
As (Select session_id,
wait_type,
wait_duration_ms,
blocking_session_id,
resource_description,
PageID = Cast(Right(resource_description, Len(resource_description)
- Charindex(':', resource_description, 3)) As Int)
From sys.dm_os_waiting_tasks
Where wait_type Like 'PAGE%LATCH_%'
And resource_description Like '2:%')
Select session_id,
wait_type,
wait_duration_ms,
blocking_session_id,
resource_description,
ResourceType = Case
When PageID = 1 Or PageID % 8088 = 0 Then 'Is PFS Page'
When PageID = 2 Or PageID % 511232 = 0 Then 'Is GAM Page'
When PageID = 3 Or (PageID - 1) % 511232 = 0 Then 'Is SGAM Page'
Else 'Is Not PFS, GAM, or SGAM page'
End
From Tasks;
이 내용에 흥미가 있습니까?
현재 기사가 여러분의 문제를 해결하지 못하는 경우 AI 엔진은 머신러닝 분석(스마트 모델이 방금 만들어져 부정확한 경우가 있을 수 있음)을 통해 가장 유사한 기사를 추천합니다:
Android Q foreground 서비스에서 위치 정보 액세스Android Q(API level29)에서 새 위치 정보 권한ACCESS_BACKGROUND_LOCATION을 추가했습니다.하지만 문서를 보더라도 특히 프론트 데스크 서비스의 동작 행위는 이해하기 어려워 조사해 봤...
텍스트를 자유롭게 공유하거나 복사할 수 있습니다.하지만 이 문서의 URL은 참조 URL로 남겨 두십시오.
CC BY-SA 2.5, CC BY-SA 3.0 및 CC BY-SA 4.0에 따라 라이센스가 부여됩니다.