Re: How to apply archived redo logfiles on a consistent database

From: Mark Bole <makbo_at_pacbell.net>
Date: Sat, 06 Mar 2004 17:08:09 GMT
Message-ID: <Zzn2c.6815$T53.2767@newssvr27.news.prodigy.com>

Sybrand Bakker wrote:
> On Sat, 6 Mar 2004 10:38:18 +0100, "Michel Cadot"
> <micadot{at}altern{dot}org> wrote:
>

 >The only difference between a physical backup and a backup to trace is
 > the actual database state. So you don't gain anything by dumping the
 > controlfile.

>>I'm afraid i'm not agree with you, the main difference physical backup and
>>dump into trace is that there is no information of the current state and thank
>>for that Oracle can recover after the date of the original database.

>
>

 >> SVRMGR> alter database backup controlfile to trace resetlogs;
 >> Statement processed.
 >

> You are wrong. You NEVER do a RESETLOGS *Prior* to incomplete
> recovery, as during incomplete recovery (using backup controlfile) the
> SCN information in the controlfile is IGNORED.
> In fact you are putting your systems at risk.
> Where in the documentation does it tell you, you need to perform a
> RESETLOGS prior to INCOMPLETE recovery?
> NOWHERE!!!!!!!!!
>
>
> --
> Sybrand Bakker, Senior Oracle DBA

The example steps posted look fine, please take another look. You both seem to be agreeing that a "create controlfile" backup has no SCN information in it.

In the example posted, I do not see an "open resetlogs" prior to incomplete recovery, I see only a "backup controlfile to trace resetlogs" (which only affects the text being written into the trace file). Creating the backup controlfile with the resetlogs option and then recovering the database with this controlfile simply ingores any existing online redo log files. Using the backup controlfile created with the resetlogs option does require a subsequent open resetlogs of the database, after recovery, as shown correctly in the example.

A situation that seems the same as that asked by the OP is documented here: "Recovering a Pre-RESETLOGS Backup"

http://download-west.oracle.com/docs/cd/A87860_01/doc/server.817/a76993/performi.htm#14918

Since Oracle recommends that you never backup online redo logs, a corollary is that when you restore an intact cold backup, even though you may have the online redo logs backed up, you are not supposed to use them, and instead open resetlogs. Then, Oracle shows you a very specific way to still use your pre-resetlogs cold backup for future recovery -- which I wouldn't trust unless I had tested it several times. It's obviously much better to simply make a new cold or hot backup after opening resetlogs, as recommended by Oracle.

If, in the OP's case, there is only a cold backup and archived redo logs, but no available physical control file newer than the one in the cold backup, I'm pretty sure the only way to get the archived redo logs rolled forward is to create a backup controlfile, as shown in the example.

--Mark Bole Received on Sat Mar 06 2004 - 11:08:09 CST