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