User-managed backups can be either logical or physical and can be backed up when cold or hot. A physical backup is a backup of a database file or archived redo log located on the operating system. A cold backup is carried out when all users are disconnected and the database is shut down completely with the commands shutdown immediate, shutdown normal or shutdown transactional. After the shutdown, all files being actively used by the database should be backed up because these files provide a complete image of the database, as it existed before shutdown. All datafiles, control files, and redo log files must be backed up during a cold backup. The database does not have to be in archive log mode, but without archive logging, the database can only be recovered to a point in time when the cold backup was done. Cold backups are reliable and hence, chances of data corruption occurring during backup are highly minimized.

While a hot backup is performed when the database is open and users are still connected to the database. The database is running in archive log mode, and this backup involves setting each tablespace into a backup state to backup the related files and then restoring the tablespace to their normal state. All datafiles, archived redo log files, and control files are backed up. The database can be fully recovered from hot backup when the archived redo logs are rolled forward or backward to any point in time. Another advantage to it is that users don’t have to worry about system shutdown during certain backup periods.

As it is with hot backups, with RMAN online backup, the database has to be in archivelog mode and open for use but restarted in mount mode. If your database is not in archivelog mode RMAN will generate an error if you try to perform an online backup. Online redo log files are never backed up by RMAN. RMAN online backup mechanism is automated and has the flexibility to backup a target portion of a tablespace incrementally, rather than backing up a whole tablespace like in User-managed backups. Like cold backups, with RMAN offline backup, the database does not have to be in archive log mode but has to be shutdown and restarted in mount mode. All datafiles, control files, and redo log files must be backed up during a offline backup. The concept of User-managed backups and RMAN backups are similar. The only difference I realized is that RMAN is more automated and equipped with a variety of task simplifying tools compared to User-managed backup utility.

Oracle Data Pump is a great and flexible tool for faster transportation of data between the databases or platforms. It has been asserted that Data Pump offers a transfer of data and metadata at twice the speed of export and twenty to thirty times the speed of the import utility. This performance improvement is derived from the use of parameter parallelism. Data Pump runs inside the database as a job, which means jobs are somewhat independent of the process that started the import or export (Surapaneni, 2006). Similar to the export and import utility, Data Pump export and import utilities are very vital in transporting large objects (table, views) from one source and importing them into a database running on a different platform. Oracle has enhanced Data Pump utility with the ability to compress the dump file sets, which can be facilitated through the use of compression parameter of the expdp command, thus making it smaller and easier to transport. The encryption_mode parameter makes your data secure, while remap_data parameter offers the ability to obfuscate data during an export or import operation. Data Pump also makes it possible to rename and partition tables, and overwrite files during an import operation.

Although they have the same purpose, Data Pump differs from the ordinary export/import utility. Export utility queries the database and writes backups of logical output (objects) to a binary file called an export dump file containing objects such as tables, views, and stored procedures. The it uses the import utility to read the export dump file and run the commands stored there to selectively bring back objects or users from the export dump file. The Export utility can run interactively through Oracle Enterprise Manager or via a command line. Export/import utility is useful to a DBA for a numbers of reasons: to perform a small-scale backup and recovery, migrating data between Oracle databases on different platforms and tablespaces between databases, upgrading databases from old versions of Oracle, detect database corruption and ensure that all the data can be read.


References:
Kuhn, D., Alapati, S., & Nanda, A. (2007). RMAN Recipes for Oracle Database 11g A Problem Solution Approach. Apress.

Rajan, C. (2007). Database Administrator II: Backup/Recovery & Network Administration. Thompson.

Velpuri, Rama. (2002). OCP Oracle9i Database: Fundamentals II Exam Guide McGraw Hill- Osborne

Nanda, Arup. Oracle Database 10g: The Top 20 Features for DBAs
http://www.oracle.com/technology/pub/articles/10gdba/pdf/10gdba_complete.pdf

Surapaneni S. October 12, 2006, Oracle 10g: Exploring Data Pump
http://www.databasejournal.com/features/oracle/article.php/3636536

Oracle Database Backup and Recovery Advanced User's Guide10g
http://www.itk.ilstu.edu/docs/Oracle/server.101/b10734/part1.htm