Oracle overview of rman backup

RMAN is a backup and recovery tool provided by Oracle. It can be used to back up and restore database files, archive logs and control files. It can also be used to perform full or incomplete database recovery. RMAN can be controlled by the command line interface or the OEM Backup Manager GUI. I personally think that one of the most important tasks of DBA is backup. when data is lost or damaged, the value of available backup can be immediately reflected, therefore, it is necessary to thoroughly study rman (I would like to thank the netizens for sharing the rman document and boobooke's video Lecture ), the following describes the basic concepts and common backup methods of rman;

1: RMAN mainly includes the following components:
Target Database: (Target Database) is the Database that requires RMAN to back up and restore it. RMAN can back up data files, control files, archive logs, and spfiles. (Note: RMAN cannot be used to back up online logs, initialize parameter files, and password files );

Server Session: (Server Session) RMAN starts the Oracle Server process on the database and creates a Session with the target database. Actual backup, restoration, and recovery operations performed by server processes on the target database;

Server process: The RMAN service process is a background process used to communicate with the RMAN tool and the database. It is also used to communicate with the RMAN tool and disk/tape and other I/O settings, the service process is responsible for all backup and recovery;

Channel: a channel is a connection between RMAN and the target database. The "allocate Channel" command starts a server process in the target database, at the same time, you must define the I/O type used by the server process for backup or recovery;
The channel control command can be used:
Controls the O/S resources used by RMAN, affecting the degree of Parallelism
Specify the I/O bandwidth limit (set the limit read rate parameter)
Define the size limit of the backup slice (set limit kbytes)
Specify the limit of the currently opened file (set limit maxopenfiles)

Recovery catalog: (recovery directory) is a database used to save backup and recovery information. It is not recommended to create a database on the target database. RMAN uses the information recorded in the recovery directory to determine how to perform the required backup and recovery operations. If the directory is not restored, the backup information can be stored in the control file of the target database;

2: Concepts
Backup Sets: features of a Backup set: includes one or more data files or archive logs, which are saved in oracle proprietary format, there is a complete collection of all the backups to form a full backup or Incremental backup;

Backup Pieces: A Backup set consists of several Backup slices. Each backup file 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 file length supported by the file system;

Image Copies Image backup: Image backup is a backup of independent files (data files, archiving logs, and control files. It is similar to file backup at the operating system level. It is neither a backup set nor a backup part, nor is it compressed;

Full backup Sets Full backup set: Full backup is a backup of data blocks used in one or more data files. Unused data blocks are not backed up, that is, oracle compresses the backup set;

Incremental backup sets Incremental backup set: Incremental backup refers to the data block that has been modified since the last or lower-level backup of one or more data files. Same as full backup, Incremental backup is also compressed;

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