Online Redo Log 結構

Structure of the Online Redo Log

Online redo log files contain redo records. A redo record is made up of a group of change vectors, each of which describes a change to a data block. For example, an update to a salary in the employees table generates a redo record that describes changes to the data segment block for the table, the undo segment data block, and the transaction table of the undo segments.

The redo records have all relevant metadata for the change, including the following:

• SCN and time stamp of the change

• Transaction ID of the transaction that generated the change

• SCN and time stamp when the transaction committed (if it committed)

• Type of operation that made the change

• Name and type of the modified data segment

  聯機重做日誌結構

  
  

  聯機重做日誌檔案中包含的重做記錄。重做記錄由一組變化向量，每一個都描述了一種改變一個資料塊。例如，在員工的工資表的更新產生重做記錄，描述變化的資料段塊表，回滾段的資料塊，undo段的事務表。

  
  

  重做記錄所有相關的後設資料的變化，包括以下內容：

  SCN和時間戳的變化

  Transaction ID 的交易產生的變化

  SCN和時間戳的事務提交時（如果它提交）

  型別操作，而改變

  修改後的資料段的名稱和型別