Log Sequence Number and Checkpoint ID

What is the difference between log sequence number and checkpoint id? How it is used for instance recovery?

Showing Answers 1 - 2 of 2 Answers

indraneel

  • Feb 2nd, 2016
 

The first one is a kind of numbering of redo-log files (and archivelog files). It is the sequence in which redo file have been used and archived log files are to be used in case of a recovery.

The last one determines the system change number of each physical database change. This number is written into the header of each datafile. If the number of any datafile does not match the other, Oracle knows this file needs recovery.

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bindu

  • Sep 8th, 2016
 

Whenever a change occurs the SCN is updated in the control file and the datafile headers, if they dont match then comes the case of recovery

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Akash Chaware

  • Dec 19th, 2016
 

A number that uniquely identifies a set of redo records in a redo log file. When Oracle fills one online redo log file and switches to a different one, Oracle automatically assigns the new file a log sequence number. For example, if you create a database with two online log files, then the first file is assigned log sequence number 1. When the first file fills and Oracle switches to the second file, it assigns log sequence number 2; when it switches back to the first file, it assigns log sequence number 3, and so forth.

When a transaction reads or writes information to the database, this occurs in memory. The Oracle memory structure that holds the blocks of data is called the Buffer Cache. ... The activity of writing changed blocks to disk is called a "checkpoint." PMON and SMON are two required background processes.

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aditya verma

  • May 11th, 2017
 

Logs sequence no is the value which is mention in header of every datafile. Below is the situations when SCN changed.
After every commit the transaction.
Log switch.
Backup completion.

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vishal gajage

  • Jun 21st, 2017
 

Log Sequence Number is assigned to every redo log file after full the redo log file....and SCN number is generated after every commit

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