Page Header Info

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 使用DBCC Page命令查看Page的context，Page Header各个字段的含义

dbcc traceon(3604)

dbcc page(DBID,TableID,IndexID,PartitionNumber)

Page Header Example

PAGE HEADER:


Page @0x000000024F382000

m_pageId = (1:164)                  m_headerVersion = 1                 m_type = 1
m_typeFlagBits = 0x0                m_level = 0                         m_flagBits = 0x0
m_objId (AllocUnitId.idObj) = 86    m_indexId (AllocUnitId.idInd) = 256 
Metadata: AllocUnitId = 72057594043564032                                
Metadata: PartitionId = 72057594039173120                                Metadata: IndexId = 1
Metadata: ObjectId = 277576027      m_prevPage = (1:163)                m_nextPage = (1:165)
pminlen = 8008                      m_slotCnt = 1                       m_freeCnt = 83
m_freeData = 8107                   m_reservedCnt = 0                   m_lsn = (34:33:14)
m_xactReserved = 0                  m_xdesId = (0:0)                    m_ghostRecCnt = 0
m_tornBits = 0                      DB Frag ID = 1            

1，m_pageId = (1:164)

Page所在的File ID 和Page ID

2，m_type = 1

 3，m_level = 0 

Page 在Index 中所处的Level，m_level=0，表示处于Leaf Level。

对于Heap，m_level=0表示的是Data Page；

对于Clustered index，m_level=0表示的是Data Page；

对于Nonclustered index，m_level=0表示的leaf level node.

4，用于计算AllocUnitId

m_objId (AllocUnitId.idObj) = 86   

m_indexId (AllocUnitId.idInd) = 256

详细信息请参考：Inside the Storage Engine: How are allocation unit IDs calculated?

5, Metadata

Metadata: AllocUnitId = 72057594043564032                               
Metadata: PartitionId = 72057594039173120                               

Metadata: IndexId = 1
Metadata: ObjectId = 277576027

6, page的chain pointer

m_prevPage = (1:163)     --Previous Page (FileID : PageID)          

m_nextPage = (1:165)　　--Next Page(FileID:PageID)

7, Other

pminlen = 8008    　　--定长数据所占的字节数为8008个字节                 

m_slotCnt = 1            --页面中的数据的行数，每页1条记录          

m_freeCnt = 83　　　 --页面中剩余的空间，还剩83字节的空间　
m_freeData = 8107    --页面空闲空间的位置在8107Byte，一个页面8KB等于8192字节             

m_reservedCnt = 0    --活动事务释放的字节数             

m_lsn = (34:33:14)   --Log Sequence No
m_xactReserved = 0  --最新加入到m_reservedCnt field的字节数            

m_xdesId = (0:0)      --添加到m_reservedCnt的最近的事务id            

m_ghostRecCnt = 0   --ghost Record count
m_tornBits = 0          --This holds either the page checksum or the bits that were displaced by the torn-page protection bits –

　　　　　　　　　　　　 depending on what form of page protection is turnde on for the database.           

参考文档：

Inside the Storage Engine: How are allocation unit IDs calculated?

Inside the Storage Engine: Anatomy of a page

笔记17 DBCC IND()非常详细解释加dbcc page([GPOSDB],1,119,3)非常详细解释 2013-1-20

Page Header Info

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原文地址：http://www.cnblogs.com/ljhdo/p/5135358.html