Recovery log

taraa

Senior Member
Persian
Does "log" mean these definitions?
6. a register of the operation of a machine.
8. any of various chronological records made concerning the use of a computer system, the changes made to data, etc.

"Recovery log: You might be wondering how it is possible to undo an update. The answer is that the system maintains a log or journal on tape or (more commonly) disk, on which details of all updates-in particular, values of updated objects (e.g.. tuples) before and after each update, sometimes called before and after images--are recorded. Thus, if it becomes necessary to undo some particular update, the system can use the corresponding log record to restore the updated object to its previous value."

An Introduction to Database Systems, 8th edition, C J Date
 
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  • entangledbank

    Senior Member
    English - South-East England
    The log is the record of all the information. It consists of multiple individual entries, each of which is a record of one event or transaction. A log is thus like a file or a list, while an individual record is like a line.
     

    taraa

    Senior Member
    Persian
    The log is the record of all the information. It consists of multiple individual entries, each of which is a record of one event or transaction. A log is thus like a file or a list, while an individual record is like a line.
    Many thanks. :):):)
     

    Egmont

    Senior Member
    English - U.S.
    Here, it refers to the log record (the line in the list) that goes with the update that should be undone.

    This gets complicated when applications use the value after the update and do something that they would not have done if the update hadn't been made or if it had been undone before the applications used it. A full discussion of that is for a database forum, not a language forum.
     

    taraa

    Senior Member
    Persian
    Here, it refers to the log record (the line in the list) that goes with the update that should be undone.

    This gets complicated when applications use the value after the update and do something that they would not have done if the update hadn't been made or if it had been undone before the applications used it. A full discussion of that is for a database forum, not a language forum.
    I understand. Many thanks. :)
     
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