11.2.0.3 to 12.1.0 (Oracle 12c) upgrade

Upgrading Oracle Database 11.2.0.3 to 12.1.0 (Oracle 12c)

There are different ways of upgrading to the latest release of Oracle database and
 Oracle provides multiple methods to upgrade. Few are listed below:

• Database Upgrade Assistant (DBUA)
• Manual Upgrade
• Transportable Tablespaces
• Datapump export/import
• Oracle Streams
• Oracle GoldenGate

I chose DBUA to upgrade my test database as it was the simplest and quickest of all. 
Below are the database environment details prior to upgrade:

Oracle Database Version:             Oracle Database 11gR2 (11.2.0.3) (64-bit)

Operating System:                         Oracle Enterprise Linux 6.1 (64-bit)

To begin the upgrade process, I copied Oracle 12c software to the database server and
 did the following

1. Backup Oracle database
2. Stop the database
3. Stop listener
4. Change ORACLE_HOME environment variable in the bash profile of “oracle” user
5. Launch Oracle 12c Installer (./runInstaller)

You will see the following screen: 

 Well, that's it. My database is now upgraded to Oracle Database 12c.

SQL> select * from v$version;

BANNER  CON_ID
---------------------------------------------------------------------------- ----------
Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production       0
PL/SQL Release 12.1.0.1.0 - Production       0
CORE 12.1.0.1.0 Production       0
TNS for Linux: Version 12.1.0.1.0 - Production       0
NLSRTL Version 12.1.0.1.0 - Production       0

SQL> 

I am sure you would like to look for alternative and near zero downtime database upgrade approaches to upgrade your production databases. Here are few of the helpful links in this regard:

• Oracle White Paper on "Upgrading to Oracle Database 12c" 
• Upgrade, Migrate, and Consolidate to Oracle Database 12c 
• Complete Checklist for Manual Upgrades to Oracle Database 12c Release 1 (12.1) [ID 1503653.1]