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SQL Server通過File Header Page來進行Crash Recovery
看了蓋總的一篇文章
http://www.eygle.com/archives/2008/11/oracle_internals_preface.html
數據文件的第一個Block記錄了重要的檢查點、SCN等信息，這些信息在啟動時要被讀取，這里就是這樣一種體現。
我們看一下SQL Server的情況，使用DBCC fileheader命令來讀取file header page，編號為10是我的一個用戶庫SSS的數據庫ID
環境：SQL Server2012 64位
SELECT DB_ID('sss') DBCC fileheader(10)
（圖一）
（圖二）
（圖三）
（圖四）
從上面的圖大家應該發現一些規律
RecoveryForkLSN：Cash Recovery的時候需要調用的lsn，也是RedoStartLSN：27000000027100001
ReadOnlyLsn：只讀模式數據庫
ReadWriteLsn：讀寫模式數據庫
因為file header page是每個數據庫的mdf文件的第一個頁面，啟動的過程里面其實最重要也是最耗時就是數據庫redo和undo過程
所以把Redo Start LSN放在file header page也就不無道理了，數據庫一啟動馬上就讀取LSN信息，然后到LDF文件里讀取日志
數據庫第0頁:file header page
數據庫第1頁：PFS (Page Free Space) ,也叫頁面自由空間
數據庫第2頁：GAM 全局分配映射(Global Allocation Map，GAM)頁面
數據庫第3頁：SGAM 共享全局分配映射(Shared Global Allocation Map，SGAM)頁面
第4頁沒有數據
第5頁沒有數據
數據庫第6頁：DCM 差異變更(Differential Changed Map，DCM)頁面
數據庫第7頁：BCM 批量更改映射（Bulk Changed Map）頁面
數據庫第8頁：sys.sysqnames 存在于每個數據庫中。
數據庫第9頁：boot page 數據庫根據這個頁面的信息來啟動的
boot page是放在第9頁不是放在第0頁，為什麼呢？因為數據庫先要進行Cash Recovery才能啟動啊
--看一下file header page DBCC TRACEON(3604,-1) GO DBCC PAGE([sss],1,0,3) GO
DBCC 執行完畢。如果 DBCC 輸出了錯誤信息，請與系統管理員聯系。 PAGE: (1:0) BUFFER: BUF @0x00000002FDABA800 bpage = 0x00000002EFF88000 bhash = 0x0000000000000000 bpageno = (1:0) bdbid = 10 breferences = 0 bcputicks = 88 bsampleCount = 1 bUse1 = 36811 bstat = 0x9 blog = 0x15ab215a bnext = 0x0000000000000000 PAGE HEADER: Page @0x00000002EFF88000 m_pageId = (1:0) m_headerVersion = 1 m_type = 15 m_typeFlagBits = 0x0 m_level = 0 m_flagBits = 0x208 m_objId (AllocUnitId.idObj) = 99 m_indexId (AllocUnitId.idInd) = 0 Metadata: AllocUnitId = 6488064 Metadata: PartitionId = 0 Metadata: IndexId = 0 Metadata: ObjectId = 99 m_prevPage = (0:0) m_nextPage = (0:0) pminlen = 0 m_slotCnt = 1 m_freeCnt = 7029 m_freeData = 7551 m_reservedCnt = 0 m_lsn = (878:901:1) m_xactReserved = 0 m_xdesId = (0:0) m_ghostRecCnt = 0 m_tornBits = -582568961 DB Frag ID = 1 Allocation Status GAM (1:2) = ALLOCATED SGAM (1:3) = NOT ALLOCATED PFS (1:1) = 0x44 ALLOCATED 100_PCT_FULL DIFF (1:6) = CHANGED ML (1:7) = NOT MIN_LOGGED File Header Data: Record Type = PRIMARY_RECORD Record Attributes = NULL_BITMAP VARIABLE_COLUMNS Record Size = 1065 Memory Dump @0x000000000D1BB956 0000000000000000: 30000800 00000000 31000000 00000000 002e007f 0.......1........... 0000000000000014: 007f0081 00830087 008b008f 0093009d 00a700b1 .................... 0000000000000028: 00b100b5 00b900bd 00c100cb 00e700f1 00fb0005 .................... 000000000000003C: 0115011f 012f0133 013d013d 01430153 01530153 ...../.3.=.=.C.S.S.S 0000000000000050: 01530153 01530153 01630163 0163016d 01770193 .S.S.S.S.c.c.c.m.w.. 0000000000000064: 019d01ad 01c901d1 012904c5 cbddcf11 44c34889 .........)......D.H. 0000000000000078: 52cc552b 3eba7601 00010080 c00500ff ffffff80 R.U+>.v............. 000000000000008C: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000000A0: 00000000 00000000 00000000 00000000 00800100 .................... 00000000000000B4: 00000000 00ffffff ff000200 001b0000 000f0100 .................... 00000000000000C8: 0001001b 0000000f 01000001 00000053 d02a7787 ...............S.*w. 00000000000000DC: 3ec94e97 926f64fe 3febf81b 000000c3 000000b2 >.N..od.?........... 00000000000000F0: 00000000 00000000 0000006e 0300006d 0300002e ...........n...m.... 0000000000000104: 00284a9c 892994c1 4692f4f1 e3c51d34 90000000 .(J..)..F......4.... 0000000000000118: 00000000 00000014 51b676d9 b1a34abc c0185ae9 ........Q.v...J...Z. 000000000000012C: 6fccb108 0000001b 0000000f 01000001 00730073 o................s.s 0000000000000140: 0073006a 49d8681b 194f469a 40c068d8 57651953 .s.jI.h..OF.@.h.We.S 0000000000000154: d02a7787 3ec94e97 926f64fe 3febf800 00000000 .*w.>.N..od.?....... 0000000000000168: 00000000 00000000 00000000 00000000 00000000 .................... 000000000000017C: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000190: 0000001b 000000c3 000000b2 006a49d8 681b194f .............jI.h..O 00000000000001A4: 469a40c0 68d85765 19000000 00000000 00000000 F.@.h.We............ 00000000000001B8: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000001CC: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000001E0: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000001F4: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000208: 00000000 00000000 00000000 00000000 00000000 .................... 000000000000021C: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000230: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000244: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000258: 00000000 00000000 00000000 00000000 00000000 .................... 000000000000026C: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000280: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000294: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000002A8: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000002BC: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000002D0: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000002E4: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000002F8: 00000000 00000000 00000000 00000000 00000000 .................... 000000000000030C: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000320: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000334: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000348: 00000000 00000000 00000000 00000000 00000000 .................... 000000000000035C: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000370: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000384: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000398: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000003AC: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000003C0: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000003D4: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000003E8: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000003FC: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000410: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000424: 00000000 00 ..... BindingID = cfddcbc5-4411-48c3-8952-cc552b3eba76 FileIdProp = 1 FileGroupId = 1 Size = 49280 MaxSize = 65535 Growth = 128 Perf = 0 BackupLsn = (0:0:0) FirstUpdateLsn = (0:0:0) OldestRestoredLsn = (0:0:0) FirstNonloggedUpdateLsn = [NULL] MinSize = 384 Status = 0 UserShrinkSize = 65535 SectorSize = 512 MaxLsn = (27:271:1) FirstLsn = (27:195:178) CreateLsn = (0:0:0) DifferentialBaseLsn = (878:877:46) DifferentialBaseGuid = 899c4a28-9429-46c1-92f4-f1e3c51d3490 FileOfflineLsn = (0:0:0) FileIdGuid = 76b65114-b1d9-4aa3-bcc0-185ae96fccb1 RestoreStatus = 8 RestoreRedoStartLsn = (27:271:1) RestoreSourceGuid = 68d8496a-191b-464f-9a40-c068d8576519 HardenedSkipLsn = [NULL] ReplTxfTruncationLsn = [NULL] TxfBackupLsn = [NULL] FstrContainerSize = [NULL] MaxLsnBranchId = 772ad053-3e87-4ec9-9792-6f64fe3febf8 SecondaryRedoStartLsn = [NULL] SecondaryDifferentialBaseLsn = [NULL] ReadOnlyLsn = (0:0:0) ReadWriteLsn = (0:0:0) RestoreDifferentialBaseLsn = (27:195:178) RestoreDifferentialBaseGuid = 68d8496a-191b-464f-9a40-c068d8576519 RestorePathOrigin hex (dec) = 0x00000000:00000000:0000 (0:0:0) m_guid = 00000000-0000-0000-0000-000000000000 DatabaseEncryptionFileState.m_maxScannedPage = 0 DatabaseEncryptionFileState.m_keyId = 0 FCBFileDEK m_dbeStatusBits = 0 m_dtCreated = 1900-01-01 00:00:00.000 m_dtLastRegenerated = 1900-01-01 00:00:00.000 m_dtLastModified = 1900-01-01 00:00:00.000 m_dtLastSet = 1900-01-01 00:00:00.000 m_dtOpened = 1900-01-01 00:00:00.000m_algId = 0 m_algId = 0 m_dwBitLen = 0 m_cbThumbprint = 0 m_rgbThumbprint = 0x DBCC 執行完畢。如果 DBCC 輸出了錯誤信息，請與系統管理員聯系。
--看一下boot page的內容 DBCC TRACEON(3604,-1) GO DBCC PAGE([sss],1,9,3) GO
Page @0x00000002EA7DE000 m_pageId = (1:9) m_headerVersion = 1 m_type = 13 m_typeFlagBits = 0x0 m_level = 0 m_flagBits = 0x200 m_objId (AllocUnitId.idObj) = 99 m_indexId (AllocUnitId.idInd) = 0 Metadata: AllocUnitId = 6488064 Metadata: PartitionId = 0 Metadata: IndexId = 0 Metadata: ObjectId = 99 m_prevPage = (0:0) m_nextPage = (0:0) pminlen = 0 m_slotCnt = 1 m_freeCnt = 6590 m_freeData = 1600 m_reservedCnt = 0 m_lsn = (878:1345:2) m_xactReserved = 0 m_xdesId = (0:0) m_ghostRecCnt = 0 m_tornBits = 2000067799 DB Frag ID = 1 Allocation Status GAM (1:2) = ALLOCATED SGAM (1:3) = NOT ALLOCATED PFS (1:1) = 0x64 MIXED_EXT ALLOCATED 100_PCT_FULL DIFF (1:6) = CHANGED ML (1:7) = NOT MIN_LOGGED Slot 0, Offset 0x60, Length 1504, DumpStyle BYTE Record Type = PRIMARY_RECORD Record Attributes = Record Size = 1504 Memory Dump @0x000000000D1BA060 0000000000000000: 0000e005 c2026302 00000000 00000000 00000000 ......c............. 0000000000000014: 00000000 00000000 00000000 00000000 08008100 .................... 0000000000000028: ae80847c bba19900 0ca30000 73007300 73002020 ...|........s.s.s. 000000000000003C: 20202020 20202020 20202020 20202020 20202020 0000000000000050: 20202020 20202020 20202020 20202020 20202020 0000000000000064: 20202020 20202020 20202020 20202020 20202020 0000000000000078: 20202020 20202020 20202020 20202020 20202020 000000000000008C: 20202020 20202020 20202020 20202020 20202020 00000000000000A0: 20202020 20202020 20202020 20202020 20202020 00000000000000B4: 20202020 20202020 20202020 20202020 20202020 00000000000000C8: 20202020 20202020 20202020 20202020 20202020 00000000000000DC: 20202020 20202020 20202020 20202020 20202020 00000000000000F0: 20202020 20202020 20202020 20202020 20202020 0000000000000104: 20202020 20202020 20202020 20202020 20202020 0000000000000118: 20202020 20202020 20202020 20202020 20202020 000000000000012C: 20202020 20202020 06000000 0a006e00 70170000 ......n.p... 0000000000000140: 00000000 00000000 00000000 00000000 6e030000 ................n... 0000000000000154: 6d030000 2e004000 6e030000 3a050000 0c000200 m.....@.n...:....... 0000000000000168: 00000000 00000000 00000000 6e030000 3a050000 ............n...:... 000000000000017C: 0c000000 c2271400 00000000 24d00000 00000000 .....'......$....... 0000000000000190: 00000041 00000000 53d02a77 873ec94e 97926f64 ...A....S.*w.>.N..od 00000000000001A4: fe3febf8 00e67dbf 00000000 00000000 00000000 .?....}............. 00000000000001B8: 00000000 1b000000 0f010000 01000000 d305e86e ...................n 00000000000001CC: 6e28d54a 892e8070 c5aec1fa 1b000000 0f010000 n(.J...p............ 00000000000001E0: 01000000 53d02a77 873ec94e 97926f64 fe3febf8 ....S.*w.>.N..od.?.. 00000000000001F4: 284a9c89 2994c146 92f4f1e3 c51d3490 14000000 (J..)..F......4..... 0000000000000208: 01006302 00000000 00000000 00000000 22000000 ..c............."... 000000000000021C: d0000000 03000400 80000000 00000000 00000000 .................... 0000000000000230: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000244: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000258: 00000000 00000000 00000000 00000000 00000000 .................... 000000000000026C: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000280: c9020000 1e000000 e3000000 c3f9a100 bda30000 .................... 0000000000000294: 00000000 00000000 00000000 00000000 553cda00 ................U<.. 00000000000002A8: 05a30000 b80b000b 00000000 59123e95 5d4a114b ............Y.>.]J.K 00000000000002BC: b9a2abb7 5245120c 00000000 00000000 00000000 ....RE.............. 00000000000002D0: 00000000 00000000 00000000 00000000 96010000 .................... 00000000000002E4: 00010000 00000000 00000000 00000000 02000000 .................... 00000000000002F8: 00000000 00000000 00000000 00000000 00000000 .................... 000000000000030C: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000320: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000334: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000348: 00000000 00000000 00000000 00000000 00000000 .................... 000000000000035C: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000370: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000384: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000398: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000003AC: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000003C0: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000003D4: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000003E8: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000003FC: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000410: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000424: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000438: 00000000 00000000 00000000 00000000 00000000 .................... 000000000000044C: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000460: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000474: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000488: 00000000 00000000 00000000 00000000 00000000 .................... 000000000000049C: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000004B0: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000004C4: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000004D8: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000004EC: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000500: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000514: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000528: 00000000 00000000 00000000 00000000 00000000 .................... 000000000000053C: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000550: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000564: 00000000 00000000 00000000 00000000 00000000 .................... 0000000000000578: 00000000 00000000 00000000 00000000 00000000 .................... 000000000000058C: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000005A0: 00000000 00000000 00000000 20000000 78000000 ............ ...x... 00000000000005B4: 43000000 00000000 00000000 00000000 00000000 C................... 00000000000005C8: 00000000 00000000 00000000 00000000 00000000 .................... 00000000000005DC: 00000000 .... DBINFO @0x000000000D1BA060 dbi_version = 706 dbi_createVersion = 611 dbi_SEVersion = 0 dbi_dvSplitPoint = 0:0:0 (0x00000000:00000000:0000) dbi_dbbackupLSN = 0:0:0 (0x00000000:00000000:0000) dbi_LastLogBackupTime = 1900-01-01 00:00:00.000 dbi_nextseqnum = 1900-01-01 00:00:00.000 dbi_status = 0x00810008 dbi_crdate = 2014-04-13 09:19:21.370dbi_dbname = sss dbi_dbid = 10 dbi_cmptlevel = 110 dbi_masterfixups = 0 dbi_maxDbTimestamp = 6000 dbi_dbbackupLSN = 0:0:0 (0x00000000:00000000:0000) dbi_RebuildLogs = 0 dbi_differentialBaseLSN = 878:877:46 (0x0000036e:0000036d:002e) dbi_RestoreFlags = 0x0040 dbi_checkptLSN = 878:1338:12 (0x0000036e:0000053a:000c) dbi_dbccFlags = 2 dbi_COWLastLSN = 0:0:0 (0x00000000:00000000:0000) dbi_DirtyPageLSN = 878:1338:12 (0x0000036e:0000053a:000c) dbi_RecoveryFlags = 0x00000000 dbi_lastxact = 0x1427c2 dbi_collation = 53284 dbi_relstat = 0x41000000 dbi_familyGUID = 772ad053-3e87-4ec9-9792-6f64fe3febf8 dbi_maxLogSpaceUsed = 3212699136 dbi_recoveryForkNameStack entry 0 hex (dec) = 0x0000001b:0000010f:0001 (27:271:1) m_guid = 6ee805d3-286e-4ad5-892e-8070c5aec1fa entry 1 hex (dec) = 0x0000001b:0000010f:0001 (27:271:1) m_guid = 772ad053-3e87-4ec9-9792-6f64fe3febf8 dbi_differentialBaseGuid = 899c4a28-9429-46c1-92f4-f1e3c51d3490 dbi_firstSysIndexes = 0001:00000014 dbi_oldestBackupXactLSN = 0:0:0 (0x00000000:00000000:0000) dbi_versionChangeLSN = 34:208:3 (0x00000022:000000d0:0003) dbi_mdUpgStat = 0x0004 dbi_category = 0x0000000000000080 dbi_safetySequence = 0 dbi_dbMirrorId = 00000000-0000-0000-0000-000000000000 dbi_pageUndoLsn = 0:0:0 (0x00000000:00000000:0000) dbi_pageUndoState = 0 dbi_disabledSequence = 0 dbi_dbmRedoLsn = 0:0:0 (0x00000000:00000000:0000) dbi_dbmOldestXactLsn = 0:0:0 (0x00000000:00000000:0000) dbi_CloneCpuCount = 0 dbi_CloneMemorySize = 0 dbi_updSysCatalog = 1900-01-01 00:00:00.000 dbi_LogBackupChainOrigin = 713:30:227 (0x000002c9:0000001e:00e3) dbi_dbccLastKnownGood = 2014-10-07 09:49:44.117 dbi_roleSequence = 0 dbi_dbmHardenedLsn = 0:0:0 (0x00000000:00000000:0000) dbi_localState = 0 dbi_safety = 0 dbi_modDate = 2014-04-06 13:14:34.310 dbi_verRDB = 184552376 dbi_lazyCommitOption = 0 dbi_svcBrokerGUID = 953e1259-4a5d-4b11-b9a2-abb75245120c dbi_svcBrokerOptions = 0x00000000 dbi_dbmLogZeroOutstanding = 0 dbi_dbmLastGoodRoleSequence = 0 dbi_dbmRedoQueue = 0 dbi_dbmRedoQueueType = 0 dbi_rmidRegistryValueDeleted = 0 dbi_dbmConnectionTimeout = 0 dbi_fragmentId = 0 dbi_AuIdNext = 1099511628182 dbi_MinSkipLsn = 0:0:0 (0x00000000:00000000:0000) dbi_commitTsOfcheckptLSN = 2 dbi_dbEmptyVersionState = 0 dbi_CurrentGeneration = 0 dbi_EncryptionHistory Scan 0 hex (dec) = 0x00000000:00000000:0000 (0:0:0) EncryptionScanInfo:ScanId = 0 Scan 1 hex (dec) = 0x00000000:00000000:0000 (0:0:0) EncryptionScanInfo:ScanId = 0 Scan 2 hex (dec) = 0x00000000:00000000:0000 (0:0:0) EncryptionScanInfo:ScanId = 0 dbi_latestVersioningUpgradeLSN = 32:120:67 (0x00000020:00000078:0043) dbi_splitAGE = 0 dbi_PendingRestoreOutcomesId = 00000000-0000-0000-0000-000000000000 dbi_ContianmentState = 0
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查看SQLSERVER內部數據頁面的小插件Internals Viewer
如有不對的地方，歡迎大家拍磚o(∩_∩)o
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