R12 Instance Home - INSTANCE_TOP

R12 architecure in brief was already introduced in my previous post, Now in this post more details on this new architecture.

In Applications release 12 top three directory structures are

db(database server),

apps(application tier servers) and

inst (instance home - new)

Figure explains these 3 directory strucures

Oracle Application release 12 introduces the concept of a top-level directory for an appication instance.

This directory referred to as Instance Home, and denoted by environment variable $INSTANCE_TOP.

This aims to get a clear distinction between the shared file system and the file system unique to an instance.

This TOP will now hold any configuration files (specific to that server), Certificates (If SSL is enabled SSL Certificates & any other certificates specific to that server) and related log files or PID files (for Apache or any other process) and INSTANCE_TOP will be specific to Server

Following are the Advantages of Instance Home

• Provides flexibility to share Applications Technology stack code (Apps, technology stack) among multiple instances/nodes and even instances (Dev,Test, Production)
• Support for read-only file systems and centralization of log files
• Enables split ownership of applications and technology stack file systems
• Improves code safety by making shared file system read-only while not patching
• Configuration and log files are co-located
• Easier collection of instance state
• Ability to use network or local storage for various file system portions
• Minimize disk usage and maximize performance