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Logical Backup : Traditional Logical Backup

Logical backup cannot be considered as main backup option.
Logical backups are useful in case of database migrations(windows to Linux vice versa).
Logical backups are more useful in case of database upgradations(9i to 10g etc).
Logical backups are platform independant.
Logical backups are useful in case of Schema level refreshes.
Logical backups are useful in case of database re org, schema re org as well as table re org.

Note : If database is down we cannot take logical backup.

In order to use exp,expdp,imp and impdp, database should be up and running.

Note : Dump files generated by exp can only be imported by imp and not by impdp.

Files generated by logical backup are :
                1.dump file
                2.log file
Dump file contains meta data as well as business data.
Dump file is partial binary and partial text in nature.
Recommanded not to edit the dump file either with vi editor or with notepad.
Logical backup takes the backup of only logical objects of the database(not going to backup CRD files).
By default, logical backup is conventional(goes thru the SGA processing layer).
We can improve the performance(minimise the backup time)by specifying direct=y.
direct=y is going to bypass the SGA processing layer and writes into operating system buffer and from the buffer writes into dump file.
The default buffer size is 64K, recommanded to specify buffers=200000.
If the dump file size is very huge and if there are n number of indexes, import by specifying indexes=no and late recreate the indexes.
By default, a user can take the backup of his/her own objects.
If a user wants to take the backup of full database, user should  have "exp_full_database" role. In the same way in order to import, user should have "imp_full_database" role.
While importing sometimes we get undo related errors. To overcome this, specify commit=y.
commit=y imports array of records and then commits rather than importing all the records and issuing commit.

Note : To suppress DDL related errors specify ignore=y.
If we specify consistant=y, oracle will not considers the objects or data that was inserted after initiating the job.
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