Backup strategy with RMAN
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  1. #1
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    Unhappy Backup strategy with RMAN

    Hi all,

    We are on Oracle 81730 on Win2000 platform.

    Until now, we were using traditional HOT/COLD and EXPORT backup strategy for backing up our production database.

    We used to take Weekly COLD and EXPORT and daily HOT backup.

    Our database size is around 50 GB.

    Now, we cannot shutdown the database so, COLD backup is out of question.

    On RMAN, we are taking level 0 (Incremental) every FRI and level 1 (Incremental differential) all remaining days. Right now, RMAN backup is stored first on the DISK and then another S/W takes it on to the tape. Daily, I have to remove RMAN backup files from the disk to free up space for new backup files.

    We also take weekly FULL EXPORT in consistent mode.

    I am not able to decide when the delete the Archive log files from the disk.

    I seek the professional advise from other experts on what should be the ideal backup strategy for this type of environment.

    Thanks in Adv.
    Sam
    ------------------------
    To handle yourself, use your head. To handle others, use your heart

  2. #2
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    I would do a archivelog all and put this rman file in the tape first. Then delete all the archive logs from the disk.

  3. #3
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    I can't understand why people insist on doing incremental backups when they backup to disk. The time to backup is still the same and the recoveries are much more difficult and lengthy. Oh well, I'm not here to judge...

    The archived redo logs can be deleted when the have been successfully backed up. Fortunately, RMAN comes with a command called "delete input". Basically, once you backup your archived log file, RMAN will delete it for you. For example, if you want to backup your archived log files and then delete them, you might:
    Code:
    ALLOCATE CHANNEL D1 TYPE DISK FORMAT '/home/oraback/al%U';
    SETLIMIT CHANNEL D1 KBYTES 2097150;
    BACKUP ARCHIVELOG ALL DELETE INPUT;
    RELEASE CHANNEL D1;
    Otherwise, if you insist on keeping your archived redo logs around, you can delete them after the next successful full hot backup (provided you have backed them up).

    50G database? I'd run a hot backup every night and take archive log backups a couple of times a day and forget about it.

    BTW, using export/import is just sucking your CPU to death for no real benefit.
    Jeff Hunter
    marist89@yahoo.com
    http://marist89.blogspot.com/
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    "I pledge to stop eating sharks fin soup and will not do so under any circumstances."

  4. #4
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    Hi Marist,

    Thanks for your help.

    I can't understand why people insist on doing incremental backups when they backup to disk.
    .

    We are doing RMAN backup to Disk temporarily until NETBACKUP is setup. Afterwards, we will backup directly on to the Tape. What other method do you suggest in place of Incremental and why Incremental is lengthy and difficult?

    Otherwise, if you insist on keeping your archived redo logs around, you can delete them after the next successful full hot backup (provided you have backed them up).50G database? I'd run a hot backup every night and take archive log backups a couple of times a day and forget about it.
    Currently, we do not take any HOT or COLD database backup. I would like to get your advise on this. Do we need to take HOT backup of the database besides the RMAN incremental level 0 and 1 backup?


    BTW, using export/import is just sucking your CPU to death for no real benefit.
    We take EXPORT on every Saturday night when noone is working on the system.

    I am new to RMAN things and currently trying to learn. So, pl. feel free to give your advise.

    I also want to know that when I take level 0 incremental backup on every Friday and then level 1 incremental backup on every day, if I need to restore database upto say last WED, do I need to first restore it from last level 0 and then only level 1 of WED?

    I am also not clear that level 0 incremental is equal to full database backup.

    Pl. help me to understand the above.

    Thanks a lot.
    Sam
    ------------------------
    To handle yourself, use your head. To handle others, use your heart

  5. #5
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  6. #6
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    Thanks Pando for the providing great link.

    Why people do not take the FULL RMAN backup and take level 0 incremental backup. Pl. tell me the diff. betw FULL and level 0 backup.

    Also, is there a need to take HOT backup besides RMAN incremental backups?

    Thanks a ton.
    Sam
    ------------------------
    To handle yourself, use your head. To handle others, use your heart

  7. #7
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    Level 0 = Full backup = Hot backup. The three terms can be used interchangeably.

    I don't have a problem with you backing up to disk, I do it myself. The major advantages to using an incremental backup are that you save space at your destination and transmit less data to your "slower" devices to write. Typically, you would want to implement incremental backups when you backup over a network to tape. Here, the bandwidth of the network is (probably) your bottleneck followed by speed at which your tape drives can stream data. Using an incremental backup will send less data to your tape devices to write.

    Using incremental backups with disk-to-disk backups (IMHO) is pointless. First, you are most likely backing up to the local machine so network speed is irrelevent. Second, your destination disks are many times faster than any tape device and therefore can handle the load. Lastly, if you are doing a full backup at some point during the week, you obviously have the space, so there's no need to save space.

    In either case, RMAN has to read through the entire database (more or less) to find out which blocks to write. Since this is the majority of the work (in a disk-to-disk backup), the time to backup will be similar in either scenario.

    Incremental restores are slow. First you have to apply the last full backup. Then you might have to apply something from an incremental backup. Then you might have to apply something from a different incremental backup. If your Mean Time To Restore (MTTR) is short, full backups are the only way to go.

    In addition, incremental restores are error prone for beginner DBAs. When you have declared a recovery, the last thing you want to do is worry about when your last successful full backup was. Save yourself the trouble and do a full backup every day.

    Lastly, don't forget to test and document your backup AND recovery scenarios. I have seen plenty of people put in backup plans only to find they can't recover when the sh#t hits the fan.
    Last edited by marist89; 01-13-2003 at 02:09 PM.
    Jeff Hunter
    marist89@yahoo.com
    http://marist89.blogspot.com/
    Get Firefox!
    "I pledge to stop eating sharks fin soup and will not do so under any circumstances."

  8. #8
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    Hi Marist,

    I have been told that with RMAN, you do not have to worry about what to restore/recover. RMAN does it itself once you tell it what to recover.

    I thought, RMAN simplifies Recovery process for the DBAs.

    I am taking Incremental, Differential (Default) backup at level 0 and 1. Level 0 on each Fri and 1 on other days.

    So, if I need to recover till Wed, first I need to restore level 0 from Fri and then level 1 from Mon,Tue and Wed. Am I right?

    Could you pl. explain me the difficulties with examples? That would be really great for me and others in forum.

    Thanks a ton!
    Sam
    ------------------------
    To handle yourself, use your head. To handle others, use your heart

  9. #9
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    Originally posted by samdba
    Hi Marist,

    I have been told that with RMAN, you do not have to worry about what to restore/recover. RMAN does it itself once you tell it what to recover.

    I thought, RMAN simplifies Recovery process for the DBAs.

    Yes, RMAN does simplify the recovery process. The problems I see with novice DBAs is they don't realize how many pieces are needed when doing a restore from a series of incremental backups.
    I am taking Incremental, Differential (Default) backup at level 0 and 1. Level 0 on each Fri and 1 on other days.

    So, if I need to recover till Wed, first I need to restore level 0 from Fri and then level 1 from Mon,Tue and Wed. Am I right?

    Sort of yes, sort of no. RMAN will know which pieces to apply, you won't have to worry about that part. However, if you have a backup piece missing between Friday (the last full) and the failure point, you might not get your data back to the failure point.

    With a series of full backups, you have a greater chance of a complete recovery.
    Jeff Hunter
    marist89@yahoo.com
    http://marist89.blogspot.com/
    Get Firefox!
    "I pledge to stop eating sharks fin soup and will not do so under any circumstances."

  10. #10
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    Oh! I think what you are saying is 'Cumulative' or FULL backup will not require to restore all the backups between 'Fri' and failing point. Right?

    But, FULL backup everyday will not take much time and disk space. Right now, we are taking the backup to disk as a temporary solution. Our long term plan is to use Veritas NETBACKUP for taking the backup directly to tape.

    Pl. suggest.

    Thanks,
    Sam
    ------------------------
    To handle yourself, use your head. To handle others, use your heart

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