I'm currently using Oracle db11g on Red Hat Enterprise Linux 5.0.
I make an incremental level 0 one time a week and incremental level 1 everyday.
I can restore this backup on my new Linux server without any problems because I have all archive logs generated after level 1 backup.
However, if online redo log is not yet filled (I mean that I have some redo info in the online log), how can I use this online log to roll forward to my restored database on the new Linux server?
I don't want to lose the valuable information that is not yet archived.
Best regards,
Sarith
Restore your backed up files.
Copy your current online redo log files (from the "damaged" production instance) to the new server.
RECOVER DATABASE;
This scenario assumes you have total continuity with archived logs and online logs. In doing the recovery, Oracle will apply necessary archived redo, then move to the online redo logs to recover to the point of failure. Important! Don't restore online redo logs from the backup you have! Use the current online logs from your crashed instance.
Finally, don't believe anything you read without practicing it for yourself!
Yes you can use the unarchived logs - if you applying the archive logs via "recover database using backup controlfile", just supply the redo log name instead of the suggested archive log name that the recovery process provides when it comes to that point (i.e. "runs out" of archive logs).
So you mean you duplicate the database to another server using RMAN?
Online redo logs are only used for disaster recovery. For instance : you lose a datafile, restore the datafile from your latest backup, and apply archivelogs and finaly the online redo logs. This makes the restored datafile have the same SCN (System change number) as the controlfile (and other datafiles). Distaster recovery complete.
When you use your backups to duplicate the database on another server you can only roll forward using your archived logs. It does a incomplete recovery by defenition (creates a new controlfile and redologs).
Do a
SQL> Alter system switch logfile
before backup?
But no matter what restore is behind the source database if it stays open. I don't now your business case exactly but DataGuard might be an option for you.
Rob
Related
I take a daily backup of my Oracle production database. The backup is created using RMAN and includes control files and archived logs up to the point the backup was taken. For disaster recovery purposes, I want to test the restore of the backup to a new server. (The production database will remain fully operational throughout.)
My question is: when I restore the backup and recover the database on the new server, is it possible to further recover it beyond the archived logs contained in the backup, by using additional archived logs that have been created on the production database since the backup was taken? If so, how would I go about this?
I've lost two hard disks yesterday . One contains an Oracle Datafile and another contains part of archive logs generated in the past 2 days. (say, arch_5.dbf and arch_6.dbf are lost, in the set of arch_1 to arch_10).
I have switched over to my standby site as part of business continuity plan.
Now, I have to recover the missed datafile. It requires the missed two archive log files for recovery.
Is is possible to apply the same set of archivelogs from standby to production, in order to recover the datafile ?
Kindly advise.
~SK~
It might prove a bit easier to
Use RMAN Incremental Backups to Refresh a Standby Database
you could use the archives that are transported to the standby site but they won't help with the recovery of the lost datafiles, unless their creation is logged in the archives.
Using the incremental backup option is easier.
I've just started a job and have identified an issue in which the database isn't currently being backed up properly so to speak. We are doing one back up every 6 hours that uses the Oracle native backup utility, but we were also sold a process by a company in which they stated that they could in essence perform "warm" backups of our database by simply taking file system copies of our database files and when we needed to restore we'd simply shut down Oracle and then copy over the files that had been copied, restart Oracle and the world would be whole again. The challenge is the fact that we have not gotten this to work just yet. I need to spend some more time reviewing the message that Oracle is giving, but my primary question is, "Is it possible" to take copies of Oracle files while Oracle is still running and to use those files at a later date to restore the database? I know that it works if the database is shut down, and then copies are made, but this is the first that I've heard that a copy (file system) can be made while the database is running. Any guidance would be greatly appreciated. Here is the error that we are getting.
ORA-00314: log 3 of thread 1, expected sequence# 1939 doesn't match 1944
ORA-00312: online log 3 thread 1: 'E:\ORACLE\ORADATA\ITMS\REDO03.LOG'
Yes, it is possible, but you have to put all the tablespaces into backup mode first and take them out afterwards (e.g. ALTER TABLESPACE x BEGIN BACKUP and ALTER TABLESPACE x END BACKUP; you'll need to check the syntax and make sure it's appropriate for your situation!). Oversimplifying hugely, this tells Oracle not to write to any of the data files, so they're all kept in a consistent state.
The two main problems you get otherwise are that individual files are updated while you're copying them so a single file can be corrupted; and more visibly that different files have different internal timestamps and sequences so Oracle won't allow them to be used.
If you're using a process you've bought in then it should already be taking care of all that though. It sounds the backup is OK and it's the restore that you haven't got working.
I haven't been involved in a restore from a hot backup for some time so someone else will need to give the detail on the actual error. My read of it is that you've tried to open with the restored data files but the later live redo logs. When restoring I think you either have to RECOVER the database using the redo logs generated since the backup was taken; or if you're trying to restore to that point in time then you can open the data with the RESETLOGS directive and lose all the changes from all the redo logs that came later. But really take more informed advice than this...
As far as I know, there are two ways that you can "copy" datafiles from a running Oracle instance.
The datafiles are copied for a
tablespace when the tablespace is in
"BEGIN BACKUP" mode.
You are using a high-end journalling
filesystem such as Veritas that can
snapshot and track block
changes on the filesystem while the
copy is taking place.
It is possible. You must must be in ARCHIVELOG mode.
An example script would be for manual:
Alter tablespace USERS begin backup;
host cp -p /u02/oradata/PROD/users01.dbf /u03/backup/PROD/
host cp -p /u02/oradata/PROD/users02.dbf /u03/backup/PROD/
Alter tablespace USERS end backup;
However, I would recommend just using RMAN. RMAN is QUITE ROBUST, included free, and will do the hot backup, as well as cold. It will clone to another instance, clone as a point in time, recover to a certain point in time, etc. Any manual backup procedure should be migrated to using the RMAN.
If you wanted to backup the entire database while it is open (I prefer as Oracle with DBA so you can avoid passwords in scripts, but ymmv):
$ ORAENV_ASK=NO
$ ORACLE_SID=PROD
$ . oraenv
$ rman target=/
Recovery Manager: Release 10.2.0.4.0 - Production on Thu Oct 28 14:23:29 2010
Copyright (c) 1982, 2007, Oracle. All rights reserved.
connected to target database: PROD (DBID=x)
RMAN> backup as compressed backupset database plus archivelog;
...
Backup Complete.
I've effectively done this with a non-mission-critical database running on Amazon EC2. My backup strategy is to periodically take a snapshot of the EBS volume. To restore a backup, I create a new EBS volume from the snapshot, start up the instance using it, then run RECOVER DATABASE.
This loses any transactions that were in-flight at the time when the snapshot was taken, of course.
Can any body give me an idea about Redo logs? An example would be most appreciated.
As Oracle changes data in a datafile, it writes out information to the redo log. In the event of a database failure, you can use this information to get the database back to the point it was before the database failure.
In a disaster recovery scenario, you could restore your last full database backup, and then apply the redo logs taken since that last backup to get the database recovered. Without those redo logs, you could only recover to the last full backup, and changes made since then would be lost.
In Oracle, you can also run in "no archive log mode", which basically means, "redo logs can be overwritten without being saved". This is generally only acceptable for a development database where you don't care about losing data since the last backup. You wouldn't typically run in this mode in a production environment, as it could be disastrous.
Here's a reference link with more info, and also an example of how you can find out the amount of generated redo.
http://www.adp-gmbh.ch/ora/concepts/redo_log.html
A definitive answer from the documentation: http://download.oracle.com/docs/cd/B19306_01/server.102/b14231/onlineredo.htm#sthref850
To expand on #dcp's answer: Technically, #dcp is referring to archived redo logs. These are optional, and as stated are only produced when running the database in archivelog mode. Every Oracle database has at least two mandatory online redo log files. These track all changes to the database. They are essential for recovery if the database crashes unexpectedly, whereas archived logs are not. Oracle uses the online redo log files to transparently bring the database back to the most recently committed state in the event of a system crash. Archived logs are used during recovery from a backup - the backup is restored, then archived logs are applied to the backup to bring the database back to it's current state or some prior point in time.
The online logs are written to in circular fashion - as one fills the next one is "swtiched" to. If archive log mode is set, then these older logs are written to the archive log destination(s). If not, they are overwritten as needed, once the changes they track are written to the datafiles.
This overview of backup and recovery at Oracle's site is pretty good to give one an idea of how the whole thing is put together.
I want to restore and recover my oracle database to the current state.
For example, I have a full backup on Sunday and I have all archive logs from Sunday to Wednesday.
If I restore and recover from backup to the new host, my database is in the state of Sunday only.
How can I apply all archive logs I have to recover my database to the state of Wednesday?
Do I need controlfile autobackup on Sunday or the current one on Wednesday?
Please give me steps to do this.
Regards, Sarith
Restore the full backup to the new server and all the new archive log files that you want to restore.
See note: 161742.1 (How To Roll Forward The Database Using a Old Control File, With Archivfiles) in metalink for a complete guide but I'm going to paraphrase it.
If you do not have access to metalink then here is the text from that note abreviated:
start db in mount mode
SQLPLUS> startup mount
Issue the command to start the recovery and apply all the archivelog files that are newer than the control/datafiles restored.
SQLPLUS> alter database recover until cancel using backup controlfile;
use this command to continue until you run out of archivelog to apply.
SQLPLUS> alter database recover continue default;
when you run out of archivelogs to apply
stop the recovery and open the database with reset logs.
SQLPLUS> alter database recover cancel;
SQLPLUS> alter database open resetlogs;
its important to take a new backup now as old archive logs will not be able to be used with this db since you've reset the logs.
As stated by the other poster, read the backup recovery manual for more info.
You haven't said what version of oracle you are using, the version you are using, and the backup strategy you have in place will effect how exactly you recover.
You need to read and understand the Backup and Recovery Manual
If this is actually a production issue, then you need to contact Oracle support right now, this isn't the time to make mistakes or learn on the job.