Basic Oracle backup and restoration knowledge literacy

Backup definition.
The fundamental purpose of backup is to restore. If needed, it can be recovered, that is, backup. For example, archive log file is a backup of online redo log file.

The validity of the backup.
Eygle said on its blog: "The system will always crash. If there is no valid backup, it will only wait for the day to die! The only thing that makes DBA wake up in a dream is that there is no valid backup ". When we use resetlogs to open a database, we recommend that you perform a full-database backup immediately to ensure that the serial number of the archive log file is continuous and the previous backup is still valid.

Backup Type.
Physical backup: Backup File
Logical backup: Backup Data

The status of the backup.
Consistent.
Inconsistent.
1) if the data file header and the control file have the same SCN, It is a consistent backup. For example, shutdown immediate is a consistent backup.
2) Creating inconsistent backups in addition to the data files and control files required for database startup, you also need to back up archive log files. Therefore, only inconsistent backups created in archive mode can be considered as valid backups.

Definition of restoration.
When the database is set to a consistent state, it is restored.

Recovery type.
Instance recovery: Read the current data file and online redo log file (Note: it is not an archive log file) to make the data file header the same as the SCN of the control file.
Media recovery: You need to use the backup created by the DBA to recover or reuse the log file.
1) instance errors usually cause two problems:
I) committed unwritten
Ii) uncommitted write
To solve these two problems, you can take two steps to restore the instance:
A) cache recovery: writes committed data. Also known as "Roll Forward"
B) transaction recovery: uncommitted revocation. Also known as "rollback"
2) Media recovery generally refers to the recovery of data files.

Recovery Method
Full recovery
Incomplete recovery
1) The recovery method that restores the required data to the latest time point is full recovery.
2) Because Incomplete recovery only uses some log files, you must specify the end mark for Oracle. As follows:
A) based on time
B) SCN-based
C) based on cancel
D) based on the log serial number

Recovery steps
Restore
Recover
1) restore is equivalent to the CP command in Linux
2) recover refers to the use of all redo log files to restore the database to the State before the crash; or, the use of some redo log files to restore the database to a specified time point.