Oracle 11.2.0.4: Basic info using RMAN for backups

backuporacleoracle-11goracle-11g-r2rman

I'm fairly new to databases. If I plan to use RMAN in archivelog mode to perform full backups each week plus incremental backups (retaining only the last 2 full backups for redundancy), how must I address the archive log files? I plan to use Oracle EM to create/manage RMAN processes, since it seems simplest.

I believe RMAN uses the archive log files to re-create changes to the database during and after the full backup occurs.

QUESTION 1

So, how far back do I need to keep the archive log files?

QUESTION 2

Does the database automatically remove the unneeded log files, or is this something I must address using cron jobs, etc.?

For example, if I do a full RMAN backup today at 1pm, can I delete all archive log files saved before 1pm? Or, will Oracle do that for me since it knows I'm doing a full backup? Or, something else?

QUESTION 3

To complete my understanding of archive logs, do I even need to put the database in archivelog mode to fully restore the database to the point in time of the RMAN backup, if I'm willing to accept loss of data from that time forward?

QUESTION 4

When RMAN finishes, and I want to copy all required backup/restore files to another server, which files need to get copied? The RMAN backup files have .bkp extension, and they need to get copied. The archive log files have .dbf extension, and they should all get copied. Anything else? (control files?)

QUESTION 5

Not sure if anyone can help answer this, but I do a lot of scientific work that uses all available digits in a binary_double number. If I choose compression for backups, will I lose accuracy when uncompressing the data? Or, is the compression algorithm going to restore the exact binary number (assuming the same operating system, etc.)?

Best Answer

QUESTION 1

So, how far back do I need to keep the archive log files?

You need to keep archive logs until you take another full backup.

If you take full backup weekly then you need to keep archive logs for week.

QUESTION 2

Does the database automatically remove the unneeded log files, or is this something I must address using cron jobs, etc.?

If you are using Fast Recovery Area for your backup and recovery purpose then Oracle will take care of it. Otherwise you need to delete it manually using RMAN commands.

For more:Configuring the Fast Recovery Area

QUESTION 3

To complete my understanding of archive logs, do I even need to put the database in archivelog mode to fully restore the database to the point in time of the RMAN backup, if I'm willing to accept loss of data from that time forward?

If you need to perform point time recovery then you need to keep archive logs, thus you are putting your database in archivelog mode. If not simply take cold backup and restore it you can not recover it since you don't have required archived logs.

QUESTION 4

When RMAN finishes, and I want to copy all required backup/restore files to another server, which files need to get copied?

You need to have control file and spfile backup which will be created automatically you have configured control file auto backup in RMAN and backup files to restore it into new host.

QUESTION 5

Not sure if anyone can help answer this, but I do a lot of scientific work that uses all available digits in a binary_double number. If I choose compression for backups, will I lose accuracy when uncompressing the data?

I have never heard or read about inaccuracy in RMAN decompression. The only disadvantage that I came across is time taken to restore the compressed RMAN backup.

Related Solutions

Extract Archived Log Files from RMAN Backupset

You probably need to use catalog, because a long time passed since January.

rman target / catalog rman_catalog_user@rman_catalog_db

RUN
{ 
  SET ARCHIVELOG DESTINATION TO '/oracle/temp_restore';
  RESTORE ARCHIVELOG FROM TIME = "to_date('2014-01-19 19:20:00','YYYY-DD-MM HH24:MI:SS')"  
                    UNTIL TIME = "to_date('2014-01-19 20:00:00','YYYY-DD-MM HH24:MI:SS')";
}

Loss of all redologs scenario

No.

The rman command 'BACKUP FULL ...' makes a backup of the datafiles but does not backup any archivelogs. If you want to backup archivlogs you have to make an archivlog backup too. This can be done by adding the 'PLUS ARCHIVLOG' clause to the 'BACKUP FULL' command or by issuing a 'BACKUP ARCHIVELOG' command after the 'BACKUP FULL' command.

Online backup of datafiles are useless if you do not have an archive log backup that covers the time of the online backup. If I understand your scenario description, you have lost all archivelogs/redologs that cover the time after 01:30 and you haven't yet made a backup of these archives. Then you can only restore the all datafiles from a backup finished before 01:30 (maybe in the previous night) and then apply all archivelogs from the beginning of this backup until 01:30. (I assume that you have a backup of all the archives generated in this period of time).

So you can recover the database until 01:30.

some consequences:
1 ) datafiles and archivelogs should be placed on different disks. If the data disk crashes you still have all archives even if you haven't backuped them to tape.
2) redo logs should not be placed only on data disks. Duplex them because they are so important. Place at least one copy to other disks than data disk.
3) backup your archive logs regularly. Even during other back operations like a long during fullbackup make the archivelog backup parallel to these operations.

Best Answer

Related Solutions

Extract Archived Log Files from RMAN Backupset

Loss of all redologs scenario

Related Question