Re: Cold & Hot backup!

In article <3b4d5e29_at_news.iprimus.com.au>, "Howard says...
>
>
>"Thomas Kyte" <tkyte_at_us.oracle.com> wrote in message
>news:9i731s029gc_at_drn.newsguy.com...
>> In article <3b4661cd_1_at_news1.prserv.net>, <hartono_nugroho_at_attglobal.net
 says...
>> >
>> >Thanks for your quick response.
>> >
>> >I want to be able to delete all of the old archive redo log files after
 I
>> >did a cold backup and start over again with the ARCHIVE redo log.
>> >My undersanding is that by using cold backup, you only need to backup the
>> >ONLINE redo log file, while in hot backup you need to have all
>> >the ARCHIVE redo log file. Or do Oracle automatically reuse the archive
>> >redo log when you issue alter tablespace begin backup command?
>> >Currently I am using only a cold backup so I don't really know the
 situation
>> >of hot backup.
>> >
>> >Regards,
>> >Ari
>> >
>>
>> wrong -- you NEVER backup online redo log files in ANY CASE.
>
>I would clarify to this extent: if you are performing COLD backups, then
>backing up the online redo logs is useful, but not essential.

it is not COLD vs HOT when talking about online redo log. Its archivelog vs noarchivelog.

I disagree totally if you are in ARCHIVELOG MODE. In that case, backing up online redo is only asking for TROUBLE. Backing it up can only make it so that it is too easy for you to overwrite your CURRENT online redo logs -- thereby making it not possible to fully perform media recovery.

Been there, seen it done. "Hey, had a failure -- its ok, we have backups. Well HURRY UP and restore them -- ok. Whoa -- why can't we recover all of our transactions? because I just overwrote the current online redo logs that hadn't been archived yet with out backups, sorry about that"....

It is *never* necessary, it just *shouldn't* be done as a matter of practice.

> The Oracle
>docs themselves says making such a backup may make recovery procedures
>easier under certain circumstances.
>

full cold backups of a database in noarchivelog mode would be the only case.

since production systems by and large must be running in archivelog mode -- the applicability of backing up online redo log is very very small.

>But, to the extent that a database once closed has *no* online files of
>whatever nature, then your statement above is actually 100% correct.
>

once closed "normally" (not shutdown aborted)

>Regards
>HJR
>
>
>

--
Thomas Kyte (tkyte@us.oracle.com)             http://asktom.oracle.com/ 
Expert one on one Oracle, programming techniques and solutions for Oracle.
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