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archive logging [message #187069] Thu, 10 August 2006 14:36 Go to next message
nandac
Messages: 41
Registered: July 2006
Location: jersey city, usa
Member

first i did a backup of the entire database.

then i enabled archive logging on my instance.

then i created a table and inserted some records into it.

i checked the directory i'd designated for archive logs - but nothing was created in it.

then i did the recovery through EM.

i saw that it was using the backup that i had taken 1 hour earlier.

but after the recovery i saw that the table i'd created after the backup was restored with the data i had inserted.

how did this happen without any file figuring in the archive log directory?
Re: archive logging [message #187083 is a reply to message #187069] Thu, 10 August 2006 16:34 Go to previous messageGo to next message
ebrian
Messages: 2794
Registered: April 2006
Senior Member
What type of recovery did you perform?

If an archive log didn't get generated, then the data was still in the online redo log.
Re: archive logging [message #187266 is a reply to message #187069] Fri, 11 August 2006 09:44 Go to previous messageGo to next message
nandac
Messages: 41
Registered: July 2006
Location: jersey city, usa
Member

maybe i'm not getting the concept right about archive log.

why do you need to archive redo logs?

especially considering there're minimum three files allocated to redo logs.

is it because once all three are full and again the first one is to be written with new data, we want to archive the old redo log data so that it might not be lost?

i created a test instance with only one table with 4 records in it. i dont think four records would have filled up 1 whole archive log file - leave alone all three.

but when i did a backup a file was created for archive log.

what gives?

appreciate any clarification here.
Re: archive logging [message #187271 is a reply to message #187069] Fri, 11 August 2006 10:02 Go to previous messageGo to next message
nandac
Messages: 41
Registered: July 2006
Location: jersey city, usa
Member

yesterday i enabled archive logging for my instance.

as mentioned before i've only one table there with four rows.

around 23:05 yesterday night it has created an file in the directory designated for archive logs.

how did this happen?

there's no transaction processing happening on the instance. i've not specified any timings for the redo logs to be archived.

appreciate the clarification.
Re: archive logging [message #187286 is a reply to message #187271] Fri, 11 August 2006 12:40 Go to previous messageGo to next message
ebrian
Messages: 2794
Registered: April 2006
Senior Member
nandac wrote on Fri, 11 August 2006 09:44

is it because once all three are full and again the first one is to be written with new data, we want to archive the old redo log data so that it might not be lost?

That's correct. It may help to read over Running a Database in ARCHIVELOG Mode.

You don't mention what type of backup you are doing, but with user managed hot-backup or RMAN hot-backup, archive logs will get generated (however, RMAN will produce significantly less).

nandac wrote on Fri, 11 August 2006 10:02

there's no transaction processing happening on the instance. i've not specified any timings for the redo logs to be archived.

There are background processes that are constantly running in your system that can also advance the SCN and thus generate additional redo & consequently archive logs.

HTH
Re: archive logging [message #187292 is a reply to message #187069] Fri, 11 August 2006 13:07 Go to previous messageGo to next message
nandac
Messages: 41
Registered: July 2006
Location: jersey city, usa
Member

brian, thanks for the clarification.

one other question : when you do a backup, is there an automatic switch of the redo logs - from the current one to the next one, even if the current one is not totally filled up.

appreciate the feedback.
Re: archive logging [message #187294 is a reply to message #187292] Fri, 11 August 2006 13:17 Go to previous message
ebrian
Messages: 2794
Registered: April 2006
Senior Member
If you are doing a BACKUP..PLUS ARCHIVELOG with 9i RMAN, the logs will be switched automatically.

If you are doing a user managed hot-backup, the logs automatically get archived when required. However, you should issue a ALTER SYSTEM ARCHIVELOG CURRENT at the end of your backup procedure to ensure all changes are captured in the archive logs. At this point, you should backup all the archive logs.
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