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.
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.
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.
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.
A variable place holder. The filespec is the pathname to the destination file for the image copy.
A variable place holder. There are three sets of values you can use for the filetype - datafile, archivelog and current controlfile.
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
An export of the entire database. There are three options: complete, cumulative and incremental.
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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.
Unique number that is used to identify a version of the database.
A backup that only includes the data blocks that have been changed.
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