SQL Server 2008記錄頭第一個位元組各部分含義

lawzjf發表於2009-08-27
SQLServer
  • Byte 0 is the TagA byte of the record metadata.

    • Bit 4 means the record has a NULL bitmap and bit 5 means the record has variable length columns. If 0x40 (bit 6) was also set, that would indicate that the record has a versioning tag. If 0x80 (bit 7) was also set, that would indicate that byte 1 has a value in it.

    • Bits 1-3 of byte 0 give the record type. The possible values are:

      • 0 = primary record. A data record in a heap that hasn't been forwarded or a data record at the leaf level of a clustered index.

      • 1 = forwarded record

      • 2 = forwarding record

      • 3 = index record

      • 4 = blob fragment

      • 5 = ghost index record

      • 6 = ghost data record

      • 7 = ghost version record. A special 15-byte record containing a single byte record header plus a 14-byte versioning tag that is used in some circumstances (like ghosting a versioned blob record)

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來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/37724/viewspace-1026436/，如需轉載，請註明出處，否則將追究法律責任。

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