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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.)?

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  • my 2 cents. To get proper incremental backups you need the enterprise version of Oracle and a block change tracking file. You don't necessarily need to keep all archive logs on disk for a week. a few days should be OK. You should have each archivelog backed up more than once for redundancy. i.e. "CONFIGURE ARCHIVELOG DELETION POLICY TO BACKED UP 2 TIMES TO DISK;" and you should use multiple channels and compression on your backups as long as you have enterprise edition. Finally, I use cron for backups, since the backups will run even if you are having an issue with enterprise manager.
    – Gandolf989
    Jan 23, 2017 at 15:04

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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.

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  • Thanks @JSapkota, Q2: How do I know if I'm using FRA or not? Is the FRA directory a predetermined file path, or something I create then tell Oracle "this is my FRA"? Q3: Is it valid to take a full cold database backup with RMAN then restore it without archivelog file(s), to at least get back to what the database was when cold backup was done? Q4: What are extensions for control file and spfile files?
    – user46688
    Jan 20, 2017 at 3:09
  • For Q2 notice the edit. Q3: yes. Q4:If you are using OMF then Oracle take cares about the name and the extension if not or if you wish you can define its format.
    – atokpas
    Jan 20, 2017 at 3:21

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