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What are different types of backup? (Hot, Cold, logical, Physical)?Cold Backup
In this type of backup, after the database is shut down, DBA exits the SVRMGR utility and copies the log files, data files and control files onto a backup media.Once the backup has been completed the DBA can restart the database.
Physical Backup
The operating system saves the database files onto tape or some other media. This is useful to restire the system to an earlier point whenever needed.
Logical Backup
In logical backup technique, the IMPORT/EXPORT utilities are used to create the backup of the database. A logical backup backs-up the contents of the database. A logical backup can be used to restore the database to the last backup. However, unlike physical back, it should not be used to create an OS back up copy because restoring using this approach would make it possible to correct the damaged datafiles. Therefore in these situations physical backups should be preferred.
Hot backup
A few systems that need to support continuous operation, it is difficult to bring down the database without interrupting the service provided to the users. In such cases, hot backup approach should be used.
There are two modes in which the hot backup works:
- ARCHIEVELOG mode
- NOARCHIVELOG mode
The database operations are suspended until archiving has been completed if the on-line redo log files are filled before they can be archived.
It is important that the directory containing the archived log files does not become full because if it does the ARCH thread wouldn't be able to archive the redo log files. The DBA has to continuously monitor the used-space percentage in the archive directory.
The database can be placed into ARCHIVELOG mode at the creation time or after the database has been created.
However, the database is shutdown before connecting as the user INTERNAL.
It was originally created in NOARCHIVELOG mode, this technique can be used to place the database in ARCHIVELOG mode
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