RMAN backup type-Backup set and Image copy)

RMAN Backup type-backup set and Image copy RMAN Backup type 1: backup set Backup set: it is the default Oracle backup type, back up used data blocks in a data file to one or more files. Such a file is called a backup file. All the backed up files are combined into a backup set ". The relationship between a backup set and a backup part is similar to that between a tablespace and a data file. A backup set is a logical concept that logically organizes the backup parts (physical files) together. Generally, a channel generates a backup set. For example, if three channels are enabled, each channel generates a backup set. However, if the control file is enabled for automatic backup, the backup file of the control file will generate a separate backup set and will not be merged with the backup set of the data file. If the number of data files contained in each backup set is specified during Backup (set through filesperset), multiple backup sets may be generated even if there is only one channel. Backup piece: Each backup piece is a separate output file. The size of a backup slice is limited. If there is no size limit, the backup set is composed of only one backup slice. The size of the backup file cannot exceed the maximum size of the files supported by your file system. The maximum size can be set through maxpiecesize: RMAN> configure channel device type disk maxpiecesize 1024 M; an independent backup set will appear after the control file is backed up. The control file and data file cannot be placed in the same backup set, because the backup set where the data file is located is in the smallest unit of volume el data blocks, and the backup set where the control file is located is in the smallest unit of the operating system block. Similarly, the backup set of the archive log file is also the smallest unit of the operating system block, so the archive log file backup set and data file backup set cannot be in the same backup set. RMAN backup type 2: Image copy (Image copy) Image Copy: similar to manual OS copy backup data files, a Data File generates an image copy file (a precise copy of database data files, archived redo logs, or control files). The difference is that this process is completed by RMAN, when RMAN is copied, it is also a data block and a data block (Oacle block). By default, it checks whether the data block is physically damaged (the logical damage check is not performed by default and must be started manually ), the tablespace does not need to be set to the begin backup state. Unlike the backup set, the generated image copy contains used data blocks and never used data blocks. The advantage of generating an image copy is that the restoration speed is faster than that of the Backup set. You do not need to copy the image during restoration. You can specify a new location. Simulation of logical damage-you can use ultraedit and other editing tools to edit the dbf file and save it after modification. Oracle also has a dedicated internal Block editing tool, BBED. You can study it later. Copy an image must at least run in the mount State (the file number in the control file must be read ). Copy an image starts with the Level0Oracle10g of the Incremental backup. You can use the single command "backupascopy" to Copy the database. Note: For image copies, the difference between RMAN and operating system copy files is that RMAN can verify the validity of the data blocks in the backup files and record the copies in the database. Differences between backup sets and backup sets-image copy and backup set ). An image copy is exactly the same as a data file, a control file, or an archived log file. You can use the operating system tool or RMAN to create an image copy, or use the operating system tool or RMAN to directly use the image copy to restore the database without any additional processing. A backup set is composed of one or more physical files called backup piece. The backup set is in RMAN's own format. The difference between a backup set and an image copy is that a backup set can contain multiple data files and can be specially processed during the backup process, such as compression or incremental backup. The backup set must be restored using RMAN.