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Difference between RMAN and EXP

On one of our systems a script is run each day which contains an EXP with
grants=y
full=y
rows=y

Some time later a RMAN is scheduled with
connect target xxx/xxx@xxx
configure retention policy to redundancy 1;
configure controlfile autobackup on;
configure device type disk parallelism 1;
run {
backup database
format 'D:\oracle\backup\xxx\DB_%s_%p.bck';
backup
(archivelog all format 'D:\oracle\backup\xxx\ARC_%s_%p.bck' delete input);
delete obsolete;
}

sql 'alter system switch logfile';
sql 'alter system switch logfile';
sql 'alter system switch logfile';
sql 'alter database backup controlfile to trace';
sql "alter database backup controlfile to ''D:\oracle\backup\xxx\Control.ctl'' reuse";


The above are done for database backup/recovery purposes.

The EXP runs at 18:00 and the RMAN at 01:00, the resulting DMP file from EXP
is orders smaller than the disk space that RMAN consumes with its backups.

What I want to know is:
1. what the differences are between EXP and RMAN?
2. Why would I choose one over the other?
3. Does it make sense to do both?
4. Is there some URL where I can get a short description of both EXP and RMAN





0
CharlesSHill
Asked:
CharlesSHill
1 Solution
 
schwertnerCommented:
RMAN uses snapshot of the contents of the .dbf files (i.e. the binary image).
RMAN is able to use and to store also the archived redo logs, so it can recover the database to the last
current state.
RMAN can do this and many other jobs for many databases.
RMAN is used for recovery of database (RMAN = Recovery Manager).
Disadvantage - complex specific command language, sometimes the principles are not clear enough,
need practice and education to be used.

EXPORT:
Does logical snapshot of the DB. This means it produces SQL scripts to create the DB objects, to input the data there.
Cannot save and use archived logs. Is used for migrations, tables replacing, i.e. for reorganization of the DB.
Nightly exports can be also used e.g. with some risk and limitations to recreate particular tables to the state
at the end of the working time (but this works only in some cases and is not universal and acceptable for serious
enterprises like banks, insurances, etc.).
0
 
boriskalavskyCommented:
1. what the differences are between EXP and RMAN?
u can use RMAN for recovery to the sertan point of time
2. Why would I choose one over the other?
if user drop table and calls you to get it back you can use IMP (import to get this table back from EXP snapshot), but it will not have any transactions that happen after that snapshot was taken. RMAN can help you with this problem too, but hole database will need to be restored on the diferent server to the time before table drop happen.
3. Does it make sense to do both?
export is an additional seafty mesure and you need to make a choice if you want it or not.
4. Is there some URL where I can get a short description of both EXP and RMAN
http://oraclesvca2.oracle.com/docs/cd/B14117_01/server.101/b10739/dba.htm#i1007021
http://download-west.oracle.com/docs/cd/B14117_01/server.101/b10742/backrest.htm#i1004902
0

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