Assuming you are just connected to RMAN via the control file as follows:
rman target /
Recovery Manager: Release 188.8.131.52.0 – Production on Tue Oct 24 15:33:56 2017
connected to target database: GGTARGET (DBID=2935137373)
RMAN generally uses channels for backups, restores and duplicates. You can define defaults for channels or over ride the defaults. There are a lot of options, here are some I use frequently.
This is a default disk channel configuration command.
CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT ‘/oracle/odump/ggtarget/%U’;
Here is another case where I override the default channel and tell RMAN where my backups are explicitly using “backup location”. This “backup location” clause can be used in many commands – not just duplicate – e.g. restore.
DUPLICATE TARGET DATABASE
BACKUP LOCATION ‘/oracle/ggtarget/backup’;
If you don’t do anything, the default may already be disk and the output will go to $ORACLE_HOME/dbs on Linux. Do an rman:
show all; # shows all rman configuration options for the given database
CONFIGURE DEFAULT DEVICE TYPE TO DISK; # defaults to disk and default path and file spec. if no other explicit commands to direct disk ouput exist then the defaults will prevail…
To explicitly write a backup to a location:
BACKUP DATABASE FORMAT=”/tmp/backup_%U”;
If you setup a FAST RECOVERY AREA using the init parameter “db_recovery_file_dest” and don’t specify where you want your disk backups – RMAN backups will be written to the FRA/backup directory.
If you put explicit channel definitions inside an RMAN run block – this will take precedence for the location and file format:
ALLOCATE CHANNEL c1 DEVICE TYPE DISK FORMAT “/disk2/%U”;
BACKUP DATABASE PLUS ARCHIVELOG delete input;
Another way to tell rman where to find backups – outside of the FRA is using the RMAN catalog start with command. It updates the controlfile or othe rman catalog if you are connected to that too with all backup pieces found in the stated directory. If in the future, you issue a command that needs those backups, the controlfile knows about them after cataloging.
catalog start with /u01/app/oracle/backup’ noprompt;
BTW, Control file creation uses it’s own specific default device / channel – unlike database and archivelog backups.
It can take some time to get familiar with RMAN due to the large number of options, defaults, device types, and channel related concepts, commands and syntax used – at least it has for me. It does not help that the tool has virtually no built help available – there is lots of online documentation though from Oracle and goggling.