Re: Apply new redo logs from original db to restored db

From: Vitalis <vitalisREMOVETHAT_at_numericable.fr>
Date: Sat, 16 Apr 2005 11:23:54 +0200
Message-Id: <pan.2005.04.16.09.23.53.578000@numericable.fr>

On Fri, 15 Apr 2005 19:20:58 -0700, hosea.basis wrote:

> Hi Jerome.
>
> One thing to note abt step 4 is that instance b is opened but that
> there are absolutely no activity at all. Therefore my understanding is
> that instance b SCN will be from the one when the copy of database was
> done. Therefore, the sub steps of step 4 will help to sync them back
> again.
>
> I agreed with you that step 4 wont work at all if instance b after
> opening the database, there are activities so that SCNs are changed.
>
> Please advise.

Hi!

The point is that even if "there are absolutely no activity at all", Oracle would have incremented the SCN upon instance startup (while doing its own tasks). And the checkpoint change number of the datafiles would have changed, thus rendering recovery impossible.

See the results in my single-user environment:

SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.

Total System Global Area 171966464 bytes

Fixed Size                   787988 bytes
Variable Size             145488364 bytes
Database Buffers           25165824 bytes
Redo Buffers                 524288 bytes

Database mounted.
SQL> select name,checkpoint_change# from v$datafile;

NAME                                                    CHECKPOINT_CHANGE#
------------------------------------------------------- ------------------
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\SYSTEM01.DBF                 1231450
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\UNDOTBS01.DBF                1231450
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\SYSAUX01.DBF                 1231450
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\USERS01.DBF                  1231450
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\EXAMPLE01.DBF                1231450

SQL> alter database open;

Database altered.

SQL> select name,checkpoint_change# from v$datafile;

NAME                                                    CHECKPOINT_CHANGE#
------------------------------------------------------- ------------------
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\SYSTEM01.DBF                 1231451
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\UNDOTBS01.DBF                1231451
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\SYSAUX01.DBF                 1231451
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\USERS01.DBF                  1231451
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\EXAMPLE01.DBF                1231451

SQL> alter system checkpoint;

System altered.

SQL> select name,checkpoint_change# from v$datafile;

NAME                                                    CHECKPOINT_CHANGE#
------------------------------------------------------- ------------------
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\SYSTEM01.DBF                 1231803
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\UNDOTBS01.DBF                1231803
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\SYSAUX01.DBF                 1231803
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\USERS01.DBF                  1231803
C:\ORACLE\PRODUCT\10.1.0\ORADATA\ORCL\EXAMPLE01.DBF                1231803

SQL> HTH
Jerome Received on Sat Apr 16 2005 - 04:23:54 CDT