Steps to Prepare Closed Database Backup in Oracle

A closed or cold database backup is an operating system backup of all the datafiles, redo log files, control file(s), parameter files, and the password file that constitute an Oracle database.

Another important RMAN feature is automatic online redo log switching. To make an open database backup of archived redo logs that includes the most recent online redo log, you can execute the BACKUP command with any of the following clauses:

1. PLUS ARCHIVELOG
2. ARCHIVELOG ALL
3. ARCHIVELOG FROM

Before beginning the backup, RMAN switches out of the current redo log group, and archives all online redo logs that have not yet been archived, up to and including the redo log group that was current when the command was issued. This feature ensures that the backup contains all redo generated before the start of the command. An effective way of backing up archived redo logs is the

BACKUP ... PLUS ARCHIVELOG

command, which causes RMAN to do the following:

1. Runs the ALTER SYSTEM ARCHIVE LOG CURRENT statement.
2. Runs BACKUP ARCHIVELOG ALL. If backup optimization is enabled, then RMAN skips logs that it has already backed up to the specified device.
3. Backs up the rest of the files specified in the BACKUP command.
4. Runs the ALTER SYSTEM ARCHIVE LOG CURRENT statement.
5. Backs up any remaining archived logs generated during the backup. If backup optimization is not enabled, then RMAN backs up the logs generated in Step 1 plus all the logs generated during the backup.
6. The preceding steps guarantee that data file backups taken during the command are recoverable to a consistent state. Furthermore, unless the online redo log is archived at the end of the backup, DUPLICATE is not possible with the backup.

Before a backup is made there are several steps you must take:

1. Perform a clean shutdowns
2. Get an up-to-date list of all files
3. Locate files

First, all datafiles must be closed with a clean shutdown procedure. If a database instance is aborted, you have to reopen it and shut it down cleanly by issuing the command

1. SHUTDOWN IMMEDIATE or
2. SHUTDOWN NORMAL.

Without a clean shutdown of the database, the backup files are inconsistent with respect to each other. This inconsistency forces Oracle to do an instance recovery on the first startup after the backup is restored. In certain failure scenarios, this automatic recovery may not be successful, and the DBA may be forced to troubleshoot. It is best to avoid this situation by ensuring the database is shut down cleanly before backup.

Second, you must get an up-to-date list of all the files for backup. Oracle datafiles belonging to a single database can reside on several disks. In order to have a complete copy of the database for database recovery, you must decide which files you need to back up. Typically you must locate and copy the following files:

Oracle Database File	File Description
Datafiles	Large binary file(s) containing data, indexes, and otherdatabase objects
Redo logs	Small, re-usable binary files that continuously receive database change information in the form of "redo entries"
Control files	Small binary file(s) containing database structure information
Parameter files	Small text file(s) containing instance startup parameters
The password file	Small, encrypted binary file containing DBA-level passwords

Next, you must determine where these files are located. Since datafiles, redo logs, and control files are database files, you can obtain information about these files by querying the data dictionary views using SQL*Plus or Server Manager. The following table gives you a list of the data dictionary views you can use to find information about the database files that you must backup:

Data Dictionary Views	Function
V$DATAFILE	Contains a list of the names and status of all datafiles
V$CONTROLFILE	Contains the names of all control files
V$LOGFILE	Contains the names of all redo log files
DBA_DATA_FILES	Contains a list of all datafiles and their respective tablespaces

The other two files, the parameter file and password file, are operating system files and are usually located in the file system of the machine on which the database server is started. A parameter file is also called init.ora with the naming convention initSID.ora. You can usually find it in ORACLE_HOME\DBS. On an NT platform, the parameter and the password files for a database named P look like this:

Parameter file:
D:\data\database\initP.ora

Password file: D:\orant\database\pwdP.ora

SQL> SELECT NAME, STATUS FROM V$DATAFILE;

The final components of the Oracle architecture consist of the physical files where our information resides on disk. Oracle has several types for data files, two of the five listed are described below.

1. Database datafiles
2. Control files
3. Online redo logs
4. Parameter files
5. Other database related files

Database Datafiles

Control files