To perform backup/restore operations on DB we suggest running the Oracle in-build tool – RMAN. Run the following commands:RMAN backup:
RMAN > backup database;RMAN restoring:
RMAN > shutdown immediate;
RMAN > restore database;
RMAN > recover database;
RMAN > startup;
By default, the Oracle Database works in NOARCHIVELOG mode, which does not allow restoring the data along with database transactions that took place between subsequent archives.
The “Backup Database” script run for Oracle working in default NOARCHIVELOG mode returns a warning about this option. Agreeing to backup in this mode results in the creation of a copy of the data (after automatically stopping and restarting the database using the script) without the possibility of restoring the above transaction.
Switching the database in ARCHIVELOG mode causes the database creation process to be performed in the background, and the archiving of the restore logs is performed in the so-called required FRA restore (FLASH RECOVERY AREA).
In this mode, the database allows to make backups without stopping the database engine, but the consumption of the FRA area increases significantly. In this case, Oracle database developers recommend moving the area in question to a separate partition, setting its size to at least 15 GB and regularly perform “backups” to prevent overflow of this area and loss of log data.
Transaction recovery log archiving mode avoids data loss, also as a result of critical media errors, the default NOARCHIVELOG option is sufficient to provide protection against operating system errors and errors of the database instance itself.
More information on the above issues can be found in the official online documentation of the ORACLE XE database:
If you need to create and restore copies of Oracle databases with user-defined settings, Oracle distributions also include a standard copy management tool, accessible from the installation directory:
– subdirectory „oraclexeapporacleproduct10.2.0serverBIN” -> „rman.exe”
– example command „rman nocatalog target XE” allows you to connect the tool to a database instance called XE (after entering the SYS user password) to make a copy
– rman command:
backup full database format „d:/backup/rman_%T_%s_%p.bus”;
allows you to create a full copy of the database in the target directory d:/backup.
Note: if the database does not work in ARCHIVELOG mode, it must be manually stopped and “mounted” using the rman command string or SQL interpreter:
After successful backup, the SQL command “alter database open;” allows you to restart the base engine.
• The basic process of restoring the last copy of the database using the rman program is limited to issuing the command string:
rman nocatalog target XE (next the SYS user password)
alter database open;
Rman command “restore database;” restores the last database archive existing in the current control file (command ‘list backup;’ – displays the content of the control file)
the recover command allows you to check the consistency of the database.
After completing the restoration process and starting the database, it is recommended to check if all necessary system spaces (tablespaces) and data files are online:
SQL > select TABLESPACE_NAME,STATUS from dba_tablespaces; SQL> select FILE#,STATUS,ENABLED,NAME from v$datafile;
Operations related to extracting control files from total copies, restoring specific arrays or so-called backup sets are more complicated issues, the description of which can be found in the source Oracle database documentation.