Friday Feb 20, 2015

Downgrade Oracle Restart 12c - Grid Infrastructure only?

Oracle RestartCan you downgrade your Oracle Restart installation from Oracle 12c back to Oracle 11g?

Actually there's no real direct downgrade supported for Oracle Restart. But of course there's a way to do it.

Basically it is: 

  • Deconfigure Oracle Restart in 12c
  • Configure Oracle Restart in 11g 

But wait a minute. It is very important to know if you have upgraded your database already. If that is the case then first you MUST downgrade your database(s) as you can't manage a higher version Oracle Database with a lower version Clusterware.

So first of all, please downgrade your Oracle database(s) first: 

At the next stage you'll need to "downgrade" the Oracle Clusterware resp Grid Infrastructure for Oracle Restart: 

Before you attempt this you'll need to deconfigure the Restart resources - and please be aware that here's a small difference in commands between Oracle and Oracle

This is from the documentation for Oracle

  • Deconfigure Oracle Restart:
    • Log in as root
    • cd /u01/app/
    • -deconfig -force
  • Once this is complete you can now deinstall the Grid Infrastructure with the deinstall tool
  • Then you will need either to reinstall the previous - for instance Oracle - Grid Infrastructure or - if it's still present on the machine - reconfigure it by running from the previous Clusterware's home
  • And finally reconfigure the database(s) again with Clusterware
    • $ srvctl downgrade database -d db-unique-name -o oraclehome -t to_version

In case you'd plan to do this exercise back from Oracle instead then you'll have different steps to follow to deconfigure Oracle Restart

  • Deconfigure Oracle Restart
    • # cd /u01/app/
    • # /u01/app/ /u01/app/ -deconfig

Regarding ASM backwards compatibility please be aware that changing the COMPATIBLE attributes within ASM will get you in trouble - see the Oracle Database Upgrade Guide for further information:


PS: See bug18160024 or the GI install guide, section A11.4 for the Standalone GI downgrade instructions from 

Thursday Jun 28, 2012

Guaranteed Restore Points as Fallback Method

Thanks to the great audience yesterday in the Upgrade & Migration Workshop in Utrecht. That was really fun and I was amazed by our new facilities (and the  "wellness" lights surrounding the plenum room's walls).

And another reason why I like to do these workshops is that often I learn new things from you :-) So credits here to Rick van  Ek who has highlighted the following topic to me. Yesterday (and in some previous workshops) I did mention during the discussion about Fallback Strategies that you'll have to switch on Flashback Database beforehand to create a guaranteed restore point in case you'll encounter an issue during the database upgrade.

I knew that we've made it possible since Oracle Database 11.2 to switch Flashback Database on without taking the database into MOUNT status (you could switch it off anyway while the database is open before in all releases). But before Oracle Database 11.2 that did require MOUNT status.

SQL> create restore point rp1 guarantee flashback database ;
create restore point rp1 guarantee flashback database
ERROR at line 1:
ORA-38784: Cannot create restore point 'RP1'.
ORA-38787: Creating the first guaranteed restore point requires mount mode when
flashback database is off

But Rick did mention that I won't need to switch Flashback Database On to create a guaranteed restore point. And he's right - in older releases I would have had to go into MOUNT state to define the restore point which meant to restart the database. But in 11.2 that's no necessary anymore. And the same will apply when you upgrade your pre-11.2 database (e.g. an Oracle Database to Oracle Database 11.2.

As soon as you start your "old" not-yet-upgraded database in your 11.2 environment with STARTUP UPGRADE you can define a guaranteed restore point. If you tail the alert.log you'll see that the database will start the RVWR (Recovery Writer) background process - you'll just have to make sure that you'd define the values for db_recovery_file_dest_size and db_recovery_file_dest.

SQL> startup upgrade
ORACLE instance started.

Total System Global Area  417546240 bytes
Fixed Size                  2228944 bytes
Variable Size             134221104 bytes
Database Buffers          272629760 bytes
Redo Buffers                8466432 bytes
Database mounted.
Database opened.
SQL> create restore point grpt guarantee flashback database;
Restore point created.
SQL> drop restore point grpt;

And don't forget to drop that restore point the sooner or later as it is guaranteed - and will fill up your Fast Recovery Area pretty quickly ;-) Just on the side: in any case archivelog mode is required if you'd like to work with restore points.

- Mike


Mike Dietrich - Oracle Mike Dietrich
Master Product Manager - Database Upgrade & Migrations - Oracle

Based in Germany. Interlink between customers/partners and the Upgrade Development. Running workshops between Arctic and Antartica. Assisting customers in their reference projects onsite and remotely. Connect via:

- -


« October 2015
Oracle related Tech Blogs
Slides Download Center
Visitors since 17-OCT-2011
White Paper and Docs
Viewlets and Videos
Workshop Map
This week on my Rega & Pono
Upgrade Reference Papers