Run multiple releases using Optimal Flexible Architecture (OFA).
Optimal Flexible Architecture (OFA) is a set of configuration guidelines for efficient and reliable Oracle Database and Oracle Grid Infrastructure deployments. Oracle recommends that you deploy all Oracle software installations in accordance with the OFA architecture standard for Oracle Database installations. Following the OFA standard helps to ensure that your installations are easier for you to maintain, and easier for you to obtain rapid assistance from Oracle Support.
OFA provides the following benefits:
Organizes large amounts of complicated software and data on disk, which can help to avoid device bottlenecks and poor performance
Facilitates routine administrative tasks, such as software and data backup functions, which are often vulnerable to data corruption
Simplifies the administration of multiple Oracle databases
Helps eliminate fragmentation of free space in the data dictionary, isolates other fragmentation, and helps to minimize resource contention
Assists database administrators to deploy an effective enterprise data management strategy
If you are not currently using the OFA standard, then switching to the OFA standard involves modifying your directory structure and relocating your database files.
For more information about OFA, refer to your operating system-specific Oracle documentation. For more information about managing data files and temp files, refer to Oracle Database Administrator’s Guide.
Databases in Multiple Oracle Homes on Separate Computers
Review if you want to connect to multiple releases using Oracle Database clients.
You can install Oracle Database 12c and Oracle Database 11g databases in Oracle homes on separate computers and Oracle Database 12c with Oracle Database 11g clients connecting to any or all of the databases. However, you must install the latest release first and install earlier releases subsequently in descending chronological order. Installing in descending chronological order ensures that each installation can find the Oracle inventory and register its installation, so that you can avoid a corruption of the Oracle inventory.
Databases in Multiple Oracle Homes on the Same Computer
Installing earlier releases of Oracle Database on the same computer that is running Oracle Database 18c can cause issues with client connections.
You can find that you are not able to install earlier releases of Oracle Database on the same computer that is running Oracle Database 18c and have clients connect to the databases of the earlier releases. For example, you cannot have Oracle Database 11g, Oracle Database 12c, and Oracle Database 18c databases in multiple (or separate) Oracle homes on the same computer and have Oracle Database 11c, Oracle Database 12c, and Oracle Database 18c clients connecting to any or all of the databases on this computer. You may be able to have a combination of some releases on one system.
Oracle recommends that you obtain the latest information on compatibility and supported configurations from My Oracle Support Note 207303.1 "Client / Server / Interoperability Support Between Different Oracle Versions" on My Oracle Support.
About the Optimal Flexible Architecture Standard
Oracle Optimal Flexible Architecture (OFA) rules help you to organize database software and configure databases to allow multiple databases, of different versions, owned by different users to coexist.
In earlier Oracle Database releases, the OFA rules provided optimal system performance by isolating fragmentation and minimizing contention. In current releases, OFA rules provide consistency in database management and support, and simplifies expanding or adding databases, or adding additional hardware.
By default, Oracle Universal Installer places Oracle Database components in directory locations and with permissions in compliance with OFA rules. Oracle recommends that you configure all Oracle components on the installation media in accordance with OFA guidelines.
Oracle recommends that you accept the OFA default. Following OFA rules is especially of value if the database is large, or if you plan to have multiple databases.
OFA assists in identification of an ORACLE_BASE with its Automatic Diagnostic Repository (ADR) diagnostic data to properly collect incidents.
About Multiple Oracle Homes Support
Oracle Database supports multiple Oracle homes. You can install this release or earlier releases of the software more than once on the same system, in different Oracle home directories.
You can install this release, or earlier releases of the software, more than once on the same system, in different Oracle home directories. However, you cannot install products from one release of Oracle Database into an Oracle home directory of a different release. For example, you cannot install Oracle Database 18c software into an existing Oracle 11g Oracle home directory.
Multiple databases, of different versions, owned by different users can coexist concurrently.
You must install a new Oracle Database release in a new Oracle home that is separate from earlier releases of Oracle Database.
You cannot install multiple releases in one Oracle home. Oracle recommends that you create a separate Oracle Database Oracle home for each release, in accordance with the Optimal Flexible Architecture (OFA) guidelines.
In production, the Oracle Database server software release must be the same as the Oracle Database dictionary release through the first four digits (the major, maintenance, and patch release number).
Later Oracle Database releases can access earlier Oracle Database releases. However, this access is only for upgrades. For example, Oracle Database 18c can access an Oracle Database 11g release 2 (18.104.22.168) database if the 22.214.171.124 database is started up in upgrade mode.
Oracle Database Client can be installed in the same Oracle Database home if both products are at the same release level. For example, you can install Oracle Database Client 126.96.36.199 into an existing Oracle Database 188.8.131.52 home but you cannot install Oracle Database Client 184.108.40.206 into an existing Oracle Database 220.127.116.11 home. If you apply a patch set before installing the client, then you must apply the patch set again.
Structured organization of directories and files, and consistent naming for database files simplify database administration.
Login home directories are not at risk when database administrators add, move, or delete Oracle home directories.
You can test software upgrades in an Oracle home in a separate directory from the Oracle home where your production database is located.