I Was Studied About Dbcc Command Family in Sql Server , During Study About Dbcc CheckAlloc , I Saw This Sentence " Checks the consistency of disk space allocation structures " , about 3 week i am searching About meaning of an allocation structure without any resaults , please help me ... What is an Allocation Structure ?
Thank you my friend , I want to know what is the concept of Allocation Structure, page & Extent are allocation structures for DataBase , But Do You Know which structures are "Disk space allocation structures" ? Thank You ,
Pages and extents are the only allocation structures in SQL Server. The transaction log has a different structure, you'll find more details on SQLSkills. I wouldn't call it an allocation structure since it's not used for reading data under normal operations.
Allocation structures are basically the pages which stores information about SQL server data and index pages. They are 1.PFS pages: Stores information about amount of free space on each page and allocation details of the page whether it is allocated or not.It also tracks whether page has ghost records or not. 2.GAM pages: Global Allocation Map pages which stores information about uniform extents whether they are available for allocation or not 3 SGAM pages: Shared Global Allocation Map this stores information about whether a mixed extent is available for being allocated or not.