Expert: Elliot Mak - 11/4/2009

Question
Hi,   

Right now, I'm configuring DG Physical Standby on two separates servers, and I have to create Standby redo logs files. Please tell me where to create them, on the Primary or on Standby server, or on both?  This standby database will only act as Read-only database, Not for switchover nor failover. We will apply redo logs Once a day during 2 or 3 hours.   

Environment:
==============
Oracle 10.2.0.3 AIX 5.3    


Thank's in advance


Mr. Elhocine Korichi
Lyon, France       

Regards

Answer
Good day

This is what I understand from your question.

(1) Configuration of DG Physical Standby
(2) Physical Standby will only act as Read-only database
(3) Need to create Standby Redo log files

In Oracle 10.2.0.3, Physical Standby cannot be opened when the database is in recovery mode.  However, you can configure your standby as a logical standby.  With physical standby, the database is in recovery mode, and it will recover the database using the redo log.  In a logical standby, the database is open and available to read, it will still use the redo log to apply the delta, however it will intrepret the redo log and apply it using SQL.  

Therefore, in order for you to have a standby database for read only, you will need to use logical standby.  If you are in Oracle 11g, then there is an addon option called Advanced DG,  it will let you to read the physical standby database while it is in recovery mode.

With regarding to the standby redo logs.  You do not need to create those standby redo logs files on the standby server.  During your configuration of your primary, one of your log_archive_dest_xx is configured to send the log to the standby server.   When the redo log is switched, it will automatic ship the log to the standby.  

For example, in the primary init.ora

log_archive_dest_1=
  'location=/oracle/flash_recovery_area/PRIM/ARCHIVELOG/
   valid_for=(all_logfiles,all_roles)
   db_unique_name=PRIM'
log_archive_dest_2=
  'service=STBY lgwr async
   valid_for=(online_logfiles,primary_roles)
   db_unique_name=STBY'

What it does is, everytime the log switch happened, it will write to the /oracle/flash_recovery_area/PRIM/ARCHIVELOG/ (log_archive_dest_1), and it also ship a copy of the redo log to my STBY standby database as specified in log_archive_dest_2.

Hope it helps.

Cheers
Elliot