R12.2 Single file system

With the release of AD and TXK Delta 6, Oracle has provided the feature of single file system on development instances for R12.2. Here's what they have mentioned in support.oracle.com article: Oracle E-Business Suite Applications DBA and Technology Stack Release Notes for R12.AD.C.Delta.6 and R12.TXK.C.Delta.6 (Doc ID 1983782.1)

Enhancements in AD and TXK Delta 6

4. New and Changed Features

Oracle E-Business Suite Technology Stack and Oracle E-Business Suite Applications DBA contain the following new or changed features in R12.AD.C.Delta.6 and R12.TXK.C.Delta.6.

4.1 Support for single file system development environments

• A normal Release 12.2 online patching environment requires one application tier file system for the run edition, and another for the patch edition. This dual file system architecture is fundamental to the patching of Oracle E-Business Suite Release 12.2 and is necessary for production environments and test environments that are meant to be representative of production. This enhancement makes it possible to have a development environment with a single file system, where custom code can be built and tested. A limited set of adop phases and modes are available to support downtime patching of such a development environment. Code should then be tested in standard dual file system test environments before being applied to production.

More details are provided in Oracle E-Business Suite Maintenance Guide, Chapter: Patching Procedures):
http://docs.oracle.com/cd/E26401_01/doc.122/e22954/T202991T531065.htm#6169002 

Support for Single File System Development Environments
A normal Release 12.2 online patching environment requires two application tier file systems, one for the run edition and another for the patch edition. This dual file system architecture is fundamental to patching of Oracle E-Business Suite Release 12.2, and is necessary both for production environments and test environments that are intended to be representative of production. This feature makes it possible to create a development environment with a single file system, where custom code can be built and tested. The code should then always be tested in a standard dual file system test environment before being applied to production.
You can set up a single file system development environment by installing Oracle E-Business Suite Release 12.2 in the normal way, and then deleting the $PATCH_BASE directory with the command:

$ rm -rf $PATCH_BASE

A limited set of adop phases and modes are available to support patching of a single file system development environment. These are:

·         apply phase in downtime mode

·         cleanup phase

Specification of any other phase or mode will cause adop to exit with an error.
The following restrictions apply to using a single file system environment:

·         You can only use a single file system environment for development purposes.

·         You cannot use online patching on a single file system environment.

·         You can only convert an existing dual file system environment to a single file system: you cannot directly create a single file system environment via Rapid Install or cloning.

·         There is no way to convert a single file system environment back into a dual file system.

·         You cannot clone from a single file system environment.