Clusterware and Database Upgrades - Expert Oracle RAC 12c - page 405

The catdwgrd.sql script under the Oracle 12c /rdbms/admin home downgrades the 12c Database components
to the previous release. If you encounter any ORA issues during the course of downgrade, fix the issue and rerun the
downgrade script once again.
After completing the script, shut down the database and exit from the SQL prompt.
Set the previous Oracle version to ORACLE_HOME, PATH OS env variables.
Start up the database in UPGRADE mode to reload the previous version components by running the catreload.sql
script from the Oracle 11g /rdbms/admin home. Examples are as follows:
export ORACLE_HOME=/u01/app/oracle/product/11.2.0/db_1
sqlplus / as sysdba
SQL> STARTUP UPGRADE
SQL> spool /tmp/dbdowngrade.log
SQL> @?/rdbms/admin/catreload.sql
Enable the CLUSTER_DATABASE parameter, and shut down and start up the database.
SQL> ALTER SYSTEM SET CLUSTER_DATABASE=TRUE SCOPE=SPFILE;
SQL> SHUTDOWN IMMEDIATE;
SQL> STARTUP
Recompile all invalid objects running the utlrp.sql script.
SQL> @?/rdbms/admin/utlr.sql
Downgrade the database version in the OCR using the srvctl downgrade command from the Oracle 12c database
home.
srvctl downgrade database -d PRDDB -o /u01/app/oracle/product/11.2.0/db_1 -to_version 11.2.0.3.0
Summary
This chapter explains the core advantages of upgrading and why an organization needs to upgrade its current (stable)
environment with new releases. Before demonstrating a two-node cluster and a RAC database upgrade with a several
hands-on examples and slide-decks, all the important prerequisites and precautions that are required for a smooth
and successful upgrade were explained. You have also learned a step-by-step procedure for downgrading a successful,
failed, or partially upgraded Clusterware and Database to the previous version.