RMAN is one of the very useful utility provided by Oracle for backup and recovery Purpose. Oracle online backups were introduced with Version 6, where tablespace must be kept in backup mode in order to take online backups.
RMAN was first introduced with Version 8 through which database server database can be backup. Since then, Oracle has enhanced RMAN features drastically by every release/version. I am not going to discuss neither the RMAN history nor the backup.
I would like to mention here, how enabling few default parameters of RMAN can save the life of dba significantly.
RMAN has following default parameters and its default values:
RMAN> show all;
using target database controlfile instead of recovery catalog
RMAN configuration parameters are:
CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default
CONFIGURE BACKUP OPTIMIZATION OFF; # default
CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
CONFIGURE CONTROLFILE AUTOBACKUP OFF; # default
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '%F'; # default
CONFIGURE DEVICE TYPE DISK PARALLELISM 1; # default
CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE MAXSETSIZE TO UNLIMITED; # default
CONFIGURE SNAPSHOT CONTROLFILE NAME TO /app/oracle/dbs/snapcf_EHEALTH.f'; # default
I would be talking the benefits of CONTROLFILE AUTOBACKUP.
By default CONTROLFILE AUTOBACKUP is OFF. I would strongly recommend enabling CONTROLFILE AUTOBACKUP ON.
I remember in my early days of DBA job, a lot of notes/articles and many people use to suggest backup the controlfile immediately after any maintenance on the tablespaces, which was a good suggestion.
RMAN just takes away this head ache of backing controlfile after any maintenance on tablespace, when you turn ON CONTROLFILE AUTOBACKUP feature.
With a control file autobackup, RMAN can recover the database even if the current control file, recovery catalog, and server parameter file are inaccessible.
A control file autobackup lets you restore the RMAN repository contained in the control file when the control file is lost and you have no recovery catalog. You do not need a recovery catalog or target database control file to restore the control file autobackup.
Whenever you add a datafile/s, resize, increase/decrease the size of datafile/s or etc, controlfile is automatically backed up.
If CONFIGURE CONTROLFILE AUTOBACKUP is ON, then RMAN automatically backs up the control file and the current server parameter file (if used to start up the database) in one of two circumstances: when a successful backup must be recorded in the RMAN repository, and when a structural change to the database affects the contents of the control file which therefore must be backed up.
You can turn the autobackup feature on or off by running the following commands through RMAN utility:CONFIGURE CONTROLFILE AUTOBACKUP ON;CONFIGURE CONTROLFILE AUTOBACKUP OFF;
Oracle documentation – backup and recovery concepts.