What is the difference between online and offline backups?
A hot (or on-line) backup is a backup performed while the database is open and available for use (read and write activity).
Except for Oracle exports, one can only do on-line backups when the database is ARCHIVELOG mode.
A cold (or off-line) backup is a backup performed while the database is off-line and unavailable to its users. Cold backups can be taken regardless
if the database is in ARCHIVELOG or NOARCHIVELOG mode.
It is easier to restore from off-line backups as no recovery (from archived logs) would be required to make the database consistent. On-line backups are less disruptive and do not require database downtime.
Point-in-time recovery (regardless if you do on-line or off-line backups) is only available when the database is in ARCHIVELOG mode.
backup_spec
A variable place holder. The backup_spec is an optional piece of syntax that is used to describe a backup set. You can specify the information such as the datafiles or tablespaces that are included in the set or the tag for the backup set. You can have more than one backup_spec for a BACKUP command, but each backup_spec has to be included within a set of parentheses.
channel_id
A variable place holder, i.e., To allocate a channel, you would use the command ALLOCATE CHANNEL channel_id TYPE type;where channel_id is a unique identifier and type is either DISK, to denote a disk file, or a specific type of third party backup device, such as a tape drive.
checksum
A checksum is created by applying a formula to a set of information to generate a unique number. Errors can be captured when
the checksum stored with the data does not equal the checksum calculated when extracting the data.
filespec
A variable place holder. The filespec is the pathname to the destination file for the image copy.
filetype
A variable place holder. There are three sets of values you can use for the filetype - datafile, archivelog and current controlfile.
formatspec
A variable placeholder. The formatspec tag can be used as part of the BACKUP command, which means it will apply to all backup specs in the command, or on an individual backup_spec. The tag can also be used in the ALLOCATE command to apply to all files which will use that
channel.
Full mode
An export of the entire database. There are three options: complete, cumulative and incremental.
Image copy
An image copy is a backup of your database. An image copy can only be written to disk. This is a physical copy so you can
choose either a datafile, archived log file or control file. All blocks are copied whether they contain data or not.
Incarnation number
Unique number that is used to identify a version of the database.
Incremental backup
A backup that only includes the data blocks that have been changed.
integer
A variable place holder, i.e., You can check whether you can use a backup set to restore the database with the Recovery Manager command
location
A variable place holder, i.e., You can also backup a control file with an SQL statement:ALTER DATABASE BACKUP CONTROLFILE TO 'location'where location is the destination for the control file backup.
Logical backup
Where you copy information from your database to a file with no regard to the physical location of data.
Oracle Clusterware
Oracle Clusterware is the cross platform cluster software required to run the Real Application Clusters (RAC) option for Oracle Database. It provides the basic clustering services at the operating system level that enable Oracle software to run in clustering mode.
Physical backup
Where you copy information from your database to a file with physical block location information stored in the backup file.
RAC
Oracle Real Application Clusters (RAC) is an option available for the Oracle Database software produced by Oracle Corporation and was introduced in 2001 with Oracle9i. RAC provides software for clustering and high availability in Oracle database environments. Oracle Corporation includes RAC with the Standard Edition when the nodes are clustered using Oracle Clusterware
redo log group
A redo log group is a collection of log files which are identical copies of each other, used to guard against log file corruption.
resetlogs
Used to reapply the archive log files to your database.
RMAN Target Database:
An RMAN Target Database is the primary database that will be backed up for RAC Grid creation. In RMAN's terminology, the term target database identifies the database that is undergoing a backup, restore or recovery operation by the RMAN Recovery Manager.
RMAN Auxiliary Database:
An Auxiliary Database is a RAC Grid that will be created as a result of the duplication of the target database. In RMAN's terminology, Auxiliary instance identifies an instance which RMAN connects in order to execute the duplicate command.
RMAN Channel:
An RMAN Channel is a communication pipeline between a RMAN executable and a target or auxiliary database. An RMAN channel consists of a server session on the target or auxiliary database and a data stream from the database to the backup device or vice-versa. RMAN console sends commands to the database using this channel, and the server session running on the database executes the command on behalf of the RMAN Recovery Manager.
RMAN Automatic Channel Allocation:
RMAN Channels can be configured to use a set of default attributes for each operation when a channel is not allocated manually. By default, RMAN configures a channel of device type, DISK, to be used for automatic channel allocation.
RMAN Manual Channel Allocation:
As the name suggests, a channel can be configured manually for special needs such as increasing the degree of parallelism. Channels can be allocated manually by using the ALLOCATE CHANNEL command in the RUN block of RMAN statement.
scriptname
A variable place holder, i.e., To run the script, you would use the same RUN command as before, but include the keywordsEXECUTE SCRIPT scriptnameinside of the braces following the command, with the scriptname indicating a unique name for the stored script.
tag
A variable place holder. The tag is an optional piece of syntax you can use to specify a name for the backup. This name is included in the information kept in the recovery catalog, so it should describe the purpose of the backup, such as 'weekly_cumulative_backup'. A tag can be reused.
type
A variable place holder. The type option is used to indicate whether the backup is a standard backup, an incremental backup (with the keyword INCREMENTAL) or a cumulative backup) with the keyword CUMULATIVE), as described earlier in this course, i.e. To allocate a channel, you would use the command ALLOCATE CHANNEL channel_id TYPE type;where channel_id is a unique identifier and type is either DISK, to denote
a disk file, or a specific type of third party backup device, such as a tape drive.
VALIDATE BACKUPSET integer
where integer is the key value for the backup set that you can get with the LIST BACKUP command in RMAN.
