Loss of Offline redo log and restore

[Former Member]

Hello!

I would like to simulate the loss of Offline redo log, and demostrate the recovery from the remote medium. There I will backup the offline redo logs.

What is the easiest recovery procedure from BRGUI can be applied and what are the technical steps?

e.g. - Restore of individual backup files

- Restore and application of arcivelog

- perhaps it is possible just to stop the DB and paste the missing redolog

from remote medium into the /saparch-directory and start the DB?

Thank you very much!

[Former Member · Accepted solution]

Thom,

Loosing an OFFLINE redo log will not cause any data inconsistency in the database, so recovery is not needed. You only have to demonstrate that you can restore the file to where it was before, ie the /oracle/SID/saparch or oracle/SID/oraarch

Some examples from SAP Help

brrestore -a 200-220

Restore the archived redo log files with the log sequence numbers from 200 through 220 into the archiving directory.

brrestore -a 40-70=/oracle/C11/sapbackup 71-90=/oracle/C11/sapreorg

Restore the archived redo log files with the log sequence numbers from 40 through 70 in directory sapbackup and those with the log sequence numbers from 71 through 90 in directory /oracle/C11/sapreorg.

brrestore -a 40-69,70-100=/oracle/C11/sapbackup

Restore the archived redo log files with the log sequence numbers from 40 through 69 in the archiving directory, and those with the log sequence numbers from 70 through 100 in directory sapbackup.

Regards

Andreas

[Former Member · Accepted solution]

Thank you Andreas,

can you also give me the technical steps/restore menus from BR*GUI and the whole sql-commandos?

Lets assume I have lost offline redo log 50, the DB is running, the remote medium is e.g. /MyRemoteBackup/Archive.

What are the steps? Should the db be shut down? When I have to copy the lost offline redo log? What is the post procedure?

Thank you in advance!

regards

Thom

[Former Member · Accepted solution]

Thom,

To restore offline redo logs from brgui, you have to go under Restore and Recovery, Resore and application of archivelog files , click on Continue, then Restore Archivelog files. You then have to put the sequence of files you want , from 50 to 60, for your case, for just one file it would be from 50 to 50 and press continue

There are no sql commands for this restore as it is just an operating system restore, no recovery is involved. The database will be up while you are doing this. No post procedure neither

I hope this helps

Andreas

[former_member204746 · Accepted solution]

to restore offline redologs, DB can stay up and running.

to restore:

brrestore -c -u / -a 50

[Former Member · Accepted solution]

Thank you very much again!

It means, if I have the current sequence 1450 and have lost the number 20, then I have to restore all redo logs from number 20 or only redo log 20?

Is the latest sequence number identified within archive log?

The redo logs can be restored from remote stage, so it is not neccessary to copy them manually, or?

What could happen If I do not have the current online redo log (1451)?

How can this file be restored?

Thank you very much!

regards

[former_member204746 · Accepted solution]

you need to restore from 20 to 1450.. that`s a lot of redologs. so, this is why you should do daily online backups to eliminate that risk.

if you lose only 1 redologs out of these 1430, you are screwed.

[Former Member · Accepted solution]

>It means, if I have the current sequence 1450 and have lost the number 20, then I >have to restore all redo logs from number 20 or only redo log 20?

Let me make sure that I understand the question correctly.

In your /oracle/SID/saparch dir, you have all 1450 offline redo logs except for number 20. If this is the case, you only need to restore one (20)

>Is the latest sequence number identified within archive log?

brrestore can identify the sequence number of each archive log

>The redo logs can be restored from remote stage, so it is not neccessary to >copy them manually, or?

No, manual copy is not required if you are using brarchive

>What could happen If I do not have the current online redo log (1451)?

>How can this file be restored?

I am a bit confused with this question, because the ONLINE redo logs do not have a sequence number like the offline ones (at least to my knowlege). If you lose the current ONLINE redo log, located under /oracle/SID/origlogA for example, say that somebody deleted it, you can get it from the /oracle/SID/mirrlogA if you used mirroring. If not, then you will have to restore from a backup and then apply all the offline redologs that you have. You can do that with

recover automatic database using backup controlfile until cancel;

or recover database using backup controlfile until time '2007-09-14:18:21:01' ;

if you know until what time you want to restore

You can not avoid losing some data then as what was in the online redo log hasn't be copied to an offline redo log

All these (and many more) are covered to the SAP Oracle course, I think registering for it will be a good investment!

Regards

Andreas

[Former Member · Accepted solution]

Hello!

Thank you for your response.

To fully understand this approach I have three simple additional quesitons:

a) Do I need Offline redo logs for the start of Oracle or are these files only necessary for the restore/recovery?

b) What is the best moment (e.g. after x succesfull full online/offlinebackups or after 1 month) to delete these files from /oraarch, in order to save free space?

c) To restore/recover the DB I always need the last offline backups generated by last consistent online backup or offline backup, is not?

Thank you very much!

regards

[Former Member · Accepted solution]

Thom,

a. You do not need them, and if somebody deletes them during the database is running, the database will still be running ok. They are only necessary for the recovery of the database

b. After you back them up sucessfully 2-3 times, I suggest that you delete them. You can set brarchive to do that automatically so that you do not run out of space in the oraarch directory

c. If you have an offline backup, you do not need any offline redo logs cause you do not have to do recovery, only restore. During the offline backup, the database is down and therefore no offline redo logs are produced

If you have an online backup that starts for example at 01:00 AM and finishes at 05:00 AM, you will need all the offline redo logs that are produced while the backup is running, that is between 01:00AM and 05:00 AM

Regards

Andreas

Message was edited by:

Andreas Malandrinos

[Former Member]

Thank you very much for the very helpful information!