Shared APPL_TOP in Oracle Apps Basics

Based on lot of request I am discussing on Shared APPL_TOP & Shared Application Tier. For next few days I will start with basics of Shared APPL_TOP like
what’s is Shared APPL_TOP ?
Advantages of Shared APPL_TOP ?
Difference between Shared APPL_TOP & Application Tier
Difference between Shared APPL_TOP & Staged APPL_TOP
How to Implement Shared APPL_TOP in Oracle Apps ?

So rather than talking too much lets start with Shared APPL_TOP & Application Tier .

In order to understand concept of shared APPL_TOP you first need to know what is APPL_TOP & what are various other TOP’s in Oracle Apps .
Oracle Apps File System (Software ) is mainly divided in to five top level directories

DATA_TOP : For data file (Database Tier )
DB_TOP : Database Software 8i, 9i or 10g ( Database Tier )

APPL_TOP : For various product tops (Application Tier )
COMMON_TOP : for files & directories common to all products ( Application Tier )
ORA_TOP : for iAS, Forms & Reports Component , Tech. Stack ( Application Tier )

Why I need shared APPL_TOP ?
If you have two/three (Multiple) Middle Tier for Large User base then you have to install APPL_TOP, COMMON_TOP & ORA_TOP equal to number of Nodes in your configuration. So if you have three middle tier then you need these three top three times & if there are n nodes you need n time these three top’s .
This result in lots of Space Requirement & bigger problem is patching so If you have 5 nodes you need to apply apps patch 5 times.
So Oracle Came Up with solution to have single APPL_TOP which is shared across all nodes in apps. This will save space as well patch timing. This concept of sharing APPL_TOP file system across all Middle Tier Nodes is called as APPL_TOP .
You will say if I can share APPL_TOP why Can’t I share COMMON_TOP & ORA_TOP as well which are also part of Application Tier , Yes you can & this concept is called as Shared Application Tier.

What is Shared Application Tier ?
Sharing Application Tier ( including APPL_TOP, COMN_TOP, ORA_TOP) across all Middle Tier Nodes in configuration is called as Shared Application Tier.

So I can say shared APPL_TOP is subset of shared Application Tier , initially shared APPL_TOP came out & based on its advantages & popularity later COMMON_TOP & ORA_TOP files were also included & entire concept is called as Shared Application Tier.

Limitation with Shared APPL_TOP , Application Tier ?
If you are running Apps on Windows you’ll be sad to hear that its not certified with Windows Operation System. More over you can share across same operation system like Linux to Linux & Solaris to Solaris.

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Source:- http://onlineappsdba.com/index.php/2006/09/19/shared-appl_top-in-oracle-apps-basics/

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