6-Maintaining Redo Log Files (2)

6-Maintaining Redo - aintaining Redo Log Files Tathagata Bhattacharjee Maintaining Redo Log Files Presenter Tathagata Bhattacharjee aintaining Redo

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: aintaining Redo Log Files Tathagata Bhattacharjee Maintaining Redo Log Files Presenter Tathagata Bhattacharjee aintaining Redo Log Files Tathagata Bhattacharjee Objectives • After completing this lesson you should be able to do the following: – Explain the purpose of online redo log files – Outline the structure of online redo log files – Control log switches and checkpoints – Multiples and maintain online redo log files – Manage online redo log files with OMF aintaining Redo Log Files Tathagata Bhattacharjee Using Redo Log Files • Redo log files record all changes made to data and provides a recovery mechanism from a system or media failure – Redo log files are organized into groups – An Oracle database requires at least two groups – Each redo log within a group is called a member aintaining Redo Log Files Tathagata Bhattacharjee Structure of Redo Log File Disk 2 Disk 1 Group 1 Group 3 Group 2 Member Member Member Member Member Member aintaining Redo Log Files Tathagata Bhattacharjee Online Redo Log Groups • A set of identical copies of online redo log files is called an online redo group • The LGWR background process concurrently writes the same information to all online redo log files in a group • The Oracle server needs a minimum of two online redo log file groups for the normal operation of a database aintaining Redo Log Files Tathagata Bhattacharjee Online Redo Log Members • Each online redo log file in a group is called a member • Each member in a group has identical log sequence numbers and the same size. The log sequence number is assigned each time the Oracle server starts writing to a log group to identify each redo log file uniquely. The current log sequence number is stored in the control file and in the header of all data files. aintaining Redo Log Files Tathagata Bhattacharjee Creating the initial Redo Log Files The initial set of online redo log groups and members are created during the database creation. –The MAXLOGFILES parameter in the CREATE DATABASE command specifies the absolute maximum of online redo log groups aintaining Redo Log Files Tathagata Bhattacharjee –The maximum and default value for MAXLOGFILES is dependent on the OS –The MAXLOGMEMBERS parameter used in the CREATE DATABASE command determines the maximum number of members per group. The maximum and default value for MAXLOGMEMBERS is dependent on the OS aintaining Redo Log Files Tathagata Bhattacharjee How Redo Logs Work • Redo logs are used in a cyclic group fashion • Each redo log file group is identified by a log sequence number that is overwritten each time the log is reused aintaining Redo Log Files...
View Full Document

This note was uploaded on 07/15/2011 for the course ECO 2023 taught by Professor Mr.raza during the Summer '10 term at FAU.

Page1 / 30

6-Maintaining Redo - aintaining Redo Log Files Tathagata Bhattacharjee Maintaining Redo Log Files Presenter Tathagata Bhattacharjee aintaining Redo

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online