Concept differences between backupsets and Images copy in Rman

Backup set Concept (Snapup set):

Oracle's default backup type, which backs up the data blocks already used in the data file to one or more files, which are called "backup slices," and all of the backed-up files are combined as "backup sets." The relationship between a backup set and a backup slice is similar to the relationship between a tablespace and a data file, and a backup set is a logical concept that logically organizes backup slices (physical files) together. In general, a channel generates a backup set, such as 3 channels, each channel is responsible for generating a backup set, but if automatic backup of control files is initiated, the backup file in which the control file resides will generate a separate backup set and will not be combined with the data file backup. The backup set where the archive log file resides is also the smallest unit of the operating system block, so the archive log file backup set and the data file backup set cannot be in the same backup set.

Image Copy Concept

Image copy: Similar to the manual OS copy backup data file, a data file generates a mirrored copy of the file (a database data file, an archive redo log, or an exact copy of the control file), unlike the process, which is done by Rman, Rman replication is also a data block of a data block (Oacle block) replication, while the default detection of data blocks for physical damage (by default, no logical corruption check, need to start manually), and do not need to set the table space to begin backup state, Unlike backup set types, the resulting mirrored copy contains used blocks of data, as well as data blocks that have never been used. Note: For mirrored replicas, the difference between Rman and the operating system copy file is that Rman is able to verify the validity of the data blocks within the backup file and record the replication in the repository.

The difference between a backup set and a mirrored copy

Mirror copy (image copy) and backup set. A mirrored copy is an exact copy of a data file (datafile), a control file, or an archive redo log file (archived log). Users can use operating system tools or Rman to create mirrored copies, and can use operating system tools or Rman to recover a database directly from a mirrored copy without any additional processing. The backup set is made up of one or more physical files called backup piece, in the form of RMAN's own format. The difference between a backup set and a mirrored copy is that the backup set can contain multiple data files, and special processing can be performed during the backup process, such as compression or incremental backups (incremental backup). The backup set must be recovered by using RMAN. Before storing to disk, backup set can use the Oracle's own binary compression algorithm to compress the data files and archive logs, and image copy does not work. The backup set does not include free blocks, and if a block is never written to data, Rman ignores the empty blocks while it is in progress, and image copy does not, so using backup set is usually faster and less space-intensive than image copy. But the overhead of image copy's restore and recover is smaller. Incremental backups can be implemented through the backup set, not through image copy. If you have an Rman driver installed for the tape, you can back up backup set directly to tape, and image copy cannot be backed up directly to tape. Both can be dumped via Rman, but backup set cannot be generated and dumped through the operating system level Rman can detect damage to 2 (corruption), and the image copy backup through the operating system tools does not check for corruption.

This article is from the Oracle all-in-one blog, so be sure to keep this source http://woquer.blog.51cto.com/9290811/1793625

Concept differences between backupsets and Images copy in Rman