Here in this section, We are giving the Introduction to Oracle database backup
What is backup?
1)A backup is a snapshot of a datafile, tablespace, or database at a certain time.
2) This copy can include important parts of a database such as the control file, redo logs and datafiles
3) A backup protects data from application error and acts as a safeguard against unexpected data loss, by providing a way to restore original data
There are two types in which Oracle database can be backed up
1)Physical backups are copies of physical database files
2) logical backups contain data that is exported using SQL commands and stored in a binary file . They are used to supplement physical backups.
Key structure for physical backups
The Key data structures of backup and recovery must be identified :
Datafiles: Every Oracle database has one or more physical datafiles that belong to logical structures called tablespaces
Control Files:Control file contains important structural information about the database like database name, timestamp of database creation, names and locations of database’s datafiles and online and archived redo log files. It also contains checkpoint information and optionally RMAN metadata
Online Redo log files:Every Oracle database contains a set of two or more online redo log files. oracle assigns every redo log file a log sequence number to uniquely identify it. Oracle uses the redo log to record all changes made to the database. Oracle records every change in a redo record, an entry in the redo buffer describing what has changed
Archived Redo log files:Archived log files are redo logs that Oracle has filled with redo entries, rendered inactive, and copied to one or more log archive destinations. Oracle can be run in either of two modes:
Automatic Managed undo:Every Oracle database must have a method of maintaining information that is used to roll back, or undo, changes to the database. Such information consists of records of the actions of transactions, primarily before they are committed
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