Log Record Structure

• Log records contain following fields

  • LSN
  • Type (CLR, update, special)
  • TransID
  • PrevLSN (LSN of prev record of this txn)
  • PageID (for update/CLRs)
  • UndoNxtLSN (for CLRs)
    • indicates which log record is being compensated
    • on later undos, log records upto UndoNxtLSN can be skipped
  • Data (redo/undo data); can be physical or logical

Notes: