Comments on: Oracle Standby redo Logs

By: SATISH NAWLE

SATISH NAWLE — Mon, 11 Aug 2008 08:43:41 +0000

Directory structure is the same on both primary and standby machines.
Backup is going locally to disk at location source_backup_directory
TNSNAMES entry STANDBY points to standby db on both machines.
TNSNAMES entry PROD points to prod db on both machines.
RMAN catalog exists, and is resolved via TNSNAMES entry rcatdb.
RMAN default channel locations.
On Source/Primary db:

su - oracle
rman target / catalog rcat_owner@rcatdb
RMAN> BACKUP CURRENT CONTROLFILE FOR STANDBY;
RMAN> BACKUP CHECK LOGICAL FULL DATABASE PLUS ARCHIVELOG;
RMAN> exit;

scp source_backup_directory oracle@standby:standby_backup_directoryOn Destination or Standby db:

sqlplus “/ as sysdba”
startup nomount
exit;On Source/Primary db:

rman target / catalog rcat_owner@rcatdb auxiliary sys@STANDBY

RMAN> DUPLICATE TARGET DATABASE FOR STANDBY NOFILENAMECHECK DORECOVER;
RMAN> exit;On Source/primary db:

show parameter log_archive_dest;
alter system set log_archive_dest_x = ‘SERVICE=STANDBY LGWR ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=PROD’;
alter system set log_archive_dest_state_x = ‘ENABLE’;On Destination or Auxiliary STANDBY:

alter system set FAL_SERVER = ‘PROD’;
alter system set FAL_CLIENT = ‘STANDBY’;

shutdown immediate;
startup nomount;
alter database mount standby database;
alter database recover managed standby database disconnect from session;To check progress:

On Primary:

column destination format a30

select dest_id,destination,status,database_mode,recovery_mode,error from V$ARCHIVE_DEST_STATUS
where status != ‘INACTIVE’;To check progress on Primary or Standby:

select * from v$managed_standby;

SATISH NAWLE
SQL STAR
9224639278

By: Andrey Goryunov

Andrey Goryunov — Thu, 16 Aug 2007 05:38:45 +0000

Hi Paul,

you are right - RMAN’s duplicate command does not do everything for you regarding standby redo logs (I am about the case when they are already created on primary database). But after duplication of the target database proper entries (taking into consideration log_file_name_convert parameter on standby side) for standby logs will be created, but without files under that. The files can be simply recreated through ALTER DATABASE CLEAR LOGFILE GROUP (n - standby log file group) command. And after that you can continue with Data Guard (or Standby) configuration.

Regards,
Andrey Goryunov

By: paulm

paulm — Thu, 16 Aug 2007 00:26:56 +0000

Indeed or you combine RAC with Dataguard and run a standby or two off the RAC cluster.

So you have the availability of RAC and the redundancy and Disaster Recovery (DR) of Dataguard.

By: jason arneil

jason arneil — Wed, 15 Aug 2007 20:13:32 +0000

I like the technique, even adding the an extra SRL over the number of redo logs. However I would dispute what you say about RAC:

“This is not the same level of redundancy or availability of Oracle RAC, but getting close.” But if your building blows up or floods, unless you have a stretched RAC cluster your dataguard solution provides you much more protection way above the availability of RAC.

jason.