Theoretical Basis of Oracle database backup and recovery

Oracle databases have three standard backup methods: Export/Import (EXPIMP), hot backup, and cold backup. Exporting spare parts is a logical backup, cold backup, and hot backup.

Oracle databases have three standard backup methods: Export/Import (EXP/IMP), hot backup, and cold backup. Exporting spare parts is a logical backup, cold backup, and hot backup.

Oracle databases have three standard backup methods: Export/Import (EXP/IMP), hot backup, and cold backup. Exporting spare parts is a logical backup, while cold backup and hot backup are physical backup.
1. Export/Import (Export/Import)
The Export can be used to extract data from the database, and the Import can be used to send the extracted data back to the Oracle database.
1. Simple Export of data (Export) and Import of data (Import)
Oracle supports three types of output:
(1) Export the data of the specified table in the T mode.
(2) user mode (U mode), which exports all objects and data of the specified user.
(3) Full database mode (Full mode). All objects in the databases are exported.
The data Import process is the inverse process of data Export (Export). The data files are imported into the database and the database data is exported to the data file respectively.
2. incremental Export/Import
Incremental export is a common data backup method. It can only be implemented for the entire database and must be exported as a SYSTEM. During this export, the system does not require any answers. The default export file name is export. dmp. If you do not want your output file to be named export. dmp, you must specify the file name to use in the command line.
Incremental export includes three types:
(1) Complete incremental Export (Complete)
Three databases are backed up, for example:
Exp system/manager inctype = complete file = 040731.dmp
(2) incremental Export
Back up the data changed after the last backup, for example:
Exp system/manager inctype = incremental file = 040731.dmp
(3) "accumulative" incremental Export
The accumulative export mode is used to export the changed information in the database after the last "full" export. For example:
Exp system/manager inctype = cumulative file = 040731.dmp
The database administrator can schedule a backup schedule and export data in three different ways.
For example, you can make the following arrangements for database blocking tasks:
Monday: Full backup ()
Tuesday: Incremental Export (B)
Wednesday: Incremental Export (C)
Thursday: Incremental Export (D)
Friday: accumulative Export (E)
Saturday: Incremental Export (F)
Sunday: Incremental Export (G)
If the database is accidentally damaged on Sunday, the database administrator can follow these steps to reply to the database:
Step 1: Use the create database Command to regenerate the DATABASE structure;
Step 2: create a large enough additional rollback.
Step 3: import A in full Increments:
Imp system/manager inctype = restore full = y FILE =
Step 4: Accumulative incremental import E:
Imp system/manager inctype = restore full = y file = E
Step 5: import the latest incremental F:
Imp system/manager inctype = restore full = y file = F
Ii. Cold backup
Cold backup occurs when the database is shut down normally. When the database is shut down normally, it will provide us with a complete database. This article describes how to copy key files to another location during cold backup. The fastest and safest way to back up Oracle information during cold backup. Advantages of cold backup:
1. It is a very fast backup method (just copy files)
2. Easy to archive (simple copy)
3. It is easy to restore to a certain point in time (you only need to copy the file back)
4. It can be combined with the archiving method to restore the database in the "best state.
5. Low maintenance and high security.
However, cold backup also has the following shortcomings:
1. When used separately, only recovery at a certain time point can be provided.
2. During the whole backup process, the database must be backed up instead of other work. That is to say, in the cold backup process, the database must be closed.
3. If the disk space is limited, it can only be copied to tape and other external storage devices, and the speed will be very slow.
4. data cannot be restored by table or by user.
If possible (mainly for efficiency), back up the information to the disk, start the database (allowing the user to work), and copy the backup information to the tape, the database can also work ). Files that must be copied in cold backup include:
1. All data files
2. All control files
3. All online redo log files
4. Init. ora file (optional)
It is worth noting that cold backup must be performed when the database is closed. When the database is turned on, the execution of database file system backup is invalid.
The following is a complete example of cold backup.
(1) shut down the database
Sqlplus/nolog
SQL>; connect/as sysdba
SQL>; shutdown normal;
(2) Use the Copy command to back up all the time files, redo log files, control files, and initialize parameter files.
SQL>; cp ;;
(3) restart the Oracle database
SQL>; startup
Iii. Hot Backup
Hot Backup is used to back up the database in archivelog mode when the database is running. Therefore, if you have a cold backup file last night and a hot backup file today, you can use this data to restore more information when a problem occurs. Hot Backup requires that the database be operated in Archivelog mode and requires a large amount of archive space. Once the database is running in the archivelog state, you can back up the database. The Hot Backup command file consists of three parts:
1. Backup of one tablespace and one tablespace in a data file.
(1) set the tablespace to the backup state.
(2) back up the data files in the tablespace
(3) restore the tablespace to the normal state.
2. Back up archive log files
(1) temporarily stop the archiving process
(2) files in the archive rede log target directory under log
(3) restart the archive Process
(4) back up the archived redo log file
3. Use the alter database bachup controlfile command to back up control files
Advantages of Hot Backup:
1. Data can be backed up at the tablespace or database file level. The backup time is short.
2. The database is still available during Backup.
3. It can be restored in seconds (to a specific point in time ).
4. Restore almost all database entities
5. Recovery is fast. In most cases, apsaradb recovers when it is still working.
Hot Backup is insufficient:
1. No error is allowed; otherwise, the consequences are serious.
2. If the Hot Backup fails, the result cannot be used for restoration at a time point.
3. Because it is difficult to maintain, you must be careful and do not allow "end with failure ".

For more information about Oracle, see the Oracle topic page? Tid = 12