Database Reference
In-Depth Information
DBUA Advantages
This section will quickly take you through some of the following advantages of DBUA over other database upgrade
options:
When a RAC database is upgraded with DBUA, the tool automatically takes appropriate
action, such as enabling, disabling CLUSTER_DATABAE parameter.
There is the option to disable the archivelog mode during the course of upgrade, to avoid
excessive archive log generation, which ultimately expedites the upgrade.
DBUA makes use of the new tools by default: initiating the catupgrd process in parallel,
running the pre-upgrade tool, etc.
Recommendations in the forms of pre/postupgrade.slq also fix any recommendation failures.
An option to recompile all objects post-database upgrade and gather pre-/post-database
statistics is provided.
The existing database listener is upgraded to the new Oracle home.
Most importantly, the tool allows you to define a recovery point to roll back the upgrade in
case of failure.
You will also have an option to migrate the database from one Oracle 12c home to another 12c
home.
Database Downgrade
Sometimes after a successful database upgrade, you might have to downgrade the database to its previous release
for various factors; hence, you should have a back-out action plan in mind when you do an upgrade procedure. The
following is the database downgrade procedure which lets you downgrade the database from 12c to a previous Oracle
database release:
Perform the current database full backup.
Disable the database vault, if it exists.
Ensure that the database COMPATIBLE initialization parameter is set to the Database version that supports a
direct upgrade (refer to Table 13-2 ).
Drop the sysman user if OEM is configured. You will have to reconfigure the OEM after you finish the downgrade
process.
Disable the CLUSTER_DATABASE initialization parameter, and stop the database as follows:
export ORACLE_SID=PRDDB1
SQL> sqlplus / as sysdba
SQL> alter system set cluster_database=false scope=spfile;
srvctl stop database -d PRDDB
Start up the database in downgrade mode and then execute the downgrade script, as follows:
SQL> STARTUP DOWNGRADE;
SQL> SPOOL /tmp/dbdowngrade.log
SQL> @?/rdbms/admin/catdwgrd.sql
 
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