Database backup, restore, Recovery theory

Backup

Cold: shuts down the database and copies the database physical files.

Hot- Standby: The database is in the open phase of the backup, through the instruction of the database file header lock, then the physical system copy, and then through the instructions to unfreeze the data file header, after thawing through the log file and undo table space content to write, the database is up to date.

RMAN Backup: block-based backup that backs up only the blocks used in the database, which is more advanced than cold standby and hot standby. Save space and time.

1) Rman memory management: Large pool is used first when backing up, if large pool is not allocated size, the shared pool memory will be consumed.

2) Rman Backup Recovery directory: The first storage path is recorded in the control file.

logical Backup (Exp/imp ): simply back up the logical structure, which is shcema. Three levels: full-Library backup, user-level backup, and table backup.

DG (physical standby, logical standby): backups can also be completed. Restores

Restore: The process of returning the backup data CP back to its original location. Return the backup file CP back to the location of your database. Cold, hot standby, Rman backups are required to restore operations. Recovery

Recovery: Recovery in archive mode makes sense, that is, you must save the log file. The process of recovery is to restore the database to the nearest process. The process of the old scn--> new SCN number. The application log is used to roll forward the SCN number.

Roll forward:

Rollback:

time-based incomplete recovery: inconvenient

Flashback Technology: find undo Table Space Rollback segment content, for data recovery, based on DML statement recovery.

Database backup, restore, Recovery theory