Release 12 will bring lots of changes to techstack. Following are the major changes

Oracle Application Server 10g components are included in the Release 12 Rapid Install
The Release 12 Rapid Install includes:
 OracleAS 10g 10.1.2 for Forms & Reports Services
 OracleAS 10g 10.1.3 for Oracle Containers for J2EE (OC4J)
The following Oracle Application Server 10g components may optionally be installed separately, using the respective Oracle Application Server 10g installation CD-ROMs:
 Single Sign-On 10g
 Oracle Internet Directory 10g
 Portal 10g
 Discoverer 10g
 Web Cache 10g
 Oracle Business Integration 10g
 Oracle BPEL Process Manager 10g
These optional services may be:
 Installed in a different ORACLE_HOME on an existing E-Business Suite Release 12 application-tier server
 Installed on a server that is physically separate from an existing E-Business Suite Release 12 Applications server

Release 12 will bring lots of changes to techstack. Following are the major changes:

1. Developer release 10g instead of 6i
2. Application server 1022 will change to Application server release 10g
3. No more mod_plsql
4. OC4J will replace jserv
5. New concept of instance home (INST_TOP)
6. Middle tier oracle homes will change from iAS to 10g based iAS 10.1.3 and Develope 6i 806 Oracle home to Developer 10g 10.1.2 home
7. New filesystem layout.

For the most comprehensive preview released so far on how the Release 12 technology stack will be architected and work, take a look at his presentation. He covers:

 Highlights of new R12 techstack components
 New Application Server 10g (10.1.2 & 10.1.3) ORACLE_HOMEs replacing the 9iAS 1.0.2.2.2 O_HOMEs from 11i
 Switch from JServ to Oracle Containers for J2EE (OC4J) for running servlets, Java Server Pages (JSP), and Enterprise Java Beans (EJB)
 OC4J Deployment details, including replacements for jserv.conf and jserv.properties configuration files
 New R12 filesystem layout, including the introduction of an Instance Home (INST_TOP)
 New use of Oracle Process Manager & Notification Server (OPMN)
 New Forms 10g deployment
 Comparison of 11i and R12 environment variables
 Discussion of relative benefits of Forms Servlet vs. Server (socket) mode deployments
 Disabled mod_plsql in R12 (more about this in a later article)
Difference between Oracle Applications 11i and 12
Database:
Database Version in 11i (11.5.9 & 11.5.10) was 9i Rel 2 where as in Release 12 its 10g R2 (10.2.0.2)
Application Tier:
Tech Stack in Application Tier consist of iAS(1.0.2.2.2) & Developer 6i (Forms & Reports 8.0.6) but in Applications R12 it is build on Fusion Middleware (10g Web Server and 10g Forms & Reports)
Sub component in Application Tier
A) HTTP Server or Web Server in R12 is Version 10.1.3 which is built on Apache version 1.3.34. In apps 11i it is Version 1.0.2.2.2 built on Apache Version 1.3.19
B) Jserv in apps 11i is replaced by OC4J (mod_jserv is replaced by mod_oc4j)
C) Forms Version 6i in Apps 11i is replaced by Forms 10.1.2.0.2 in R12
D) Reports Version 6i in Apps 11i is replaced by Reports 10.1.2.0.2 in R12
E) JDBC version is changed from version 9 in apps 11i to version 10.2.0 in Apps R12
F) modplsql or mod_pls is removed from Apps R12 (What will happen to my mod plsql applications- coming soon* )
G) Java processes use JDK/JRE version 1.5.0 in R12 against JDK version 1.3.1 or 1.4.2 in Apps 11i
H) For various environment variable changes check below picture


Application Tier File System Architecture


Overview of R12 Application File System
A multi-node installation of Release 12 supports both shared and non-shared application tier file systems. An application tier file system consists of:
• APPL_TOP file system (APPL_TOP and COMMON_TOP directories).
• Application tier technology stack file system (OracleAS 10.1.2 and 10.1.3 Oracle Homes).
• Instance Home (INST_TOP) file system. Each application tier has a unique Instance Home file system associated with it.
Major Application Tier Services:

- Root services
- Web Entry Point services
- Web Application services
- Batch Processing services
- Other services

Application Tier-Node

Note:Installed and Configured Services
1. APPL_TOP
2. COMMON_TOP
3. OracleAS 10.1.2 ORACLE_HOME
4. OracleAS 10.1.3 ORACLE_HOME

Instance Home

Note: Top-level directory that contains instance-specific files associated with an Application Tier.
- APPL_TOP
- COMMON_TOP
- OracleAS 10.1.2 ORACLE_HOME
- OracleAS 10.1.3 ORACLE_HOME
- log files
- pid files
- certificates files

Oracle Applications/E-Business Suite Release 12 introduces a new concept of a top-level directory for an Applications Instance which is known as Instance Home and is denoted the environment variable $INST_TOP.
Instance Home contains all the config files, log files, SSL certificates etc.

Advantages of new INSTANCE HOME
• The additional Instance Home makes the middle tier more easy to manage and organised since the data is kept separate from the config files. The Instance Home also has the ability to share the Applications and Technology stack code across multiple instances.
• Another advantage of the Instance Home is that the Autoconfig no longer writes anything to the APPL_TOP and ORACLE_HOME directories, everything is now written in the INST_TOP as a result APPL_TOP and ORACLE_HOME can also be made read only file system if required .
• Earlier say the adpatch used to write the log file in APPL_TOP/admin directory but with the new model the APPL_CONFIG_HOME/admin is used. To create a new instance that shares an existing middle-tier, just create a new instance_top with proper config files and NFS Mount the middle tier in the server.
• The basic structure of the Instance Home is:$APPS_BASE/inst/apps/$CONTEXT_NAME or also defined by environment variable $INST_TOP, where APPS_BASE (which does not have or need a corresponding environment variable) is the top level of the Applications installation and $CONTEXT_NAME is the highest level at which the Applications context exists (format $SID_$hostname).

Instance Home Directory Structure
$INST_TOP/admin/scripts ($ADMIN_SCRIPTS_HOME): All AD scripts are located here
$INST_TOP/appl ($APPL_CONFIG_HOME) : For standalone envs, this is set to $APPL_TOP
$INST_TOP/appl/fnd/12.0.0/secure FND_SECURE: The dbc file is located here
$INST_TOP/appl/admin All the env config files are located here $INST_TOP/certs SSL Certificates go here $INST_TOP/logs LOG_HOME: Central log file location. All log files are placed here (except adconfig)
$INST_TOP/logs/ora ($ORA_CONFIG_HOME)
$INST_TOP/logs/ora/10.1.2 ‘C’ Oracle home config, Contains tnsnames and forms listener servlet config files
$INST_TOP/logs/ora/10.1.3 Apache & OC4J config home, Apache, OC4J and opmn. This is the ‘Java’ oracle home configuration for OPMN, Apache and OC4J $INST_TOP/pids Apache/Forms server PID files are located here $INST_TOP/portal Apache’s DocumentRoot folder

Oracle R12/12i log file (Patch, Clone, Startup/Shutdown)

Log files are useful in troubleshooting issues in Oracle Applications. Here is the list of Log file location in Oracle Applications for Startup/Shutdown, Cloning, Patching, DB & Apps Listener and various components in Apps R12/12i:

Startup/Shutdown Log files for Application Tier in R12
Instance Top is new TOP added in R12
Startup/Shutdown error message text files like adapcctl.txt, adcmctl.txt
$INST_TOP/apps/$CONTEXT_NAME/logs/appl/admin/log
Startup/Shutdown error message related to tech stack (10.1.2, 10.1.3 forms/reports/web)
$INST_TOP/apps/$CONTEXT_NAME/logs/ora/ (10.1.2 & 10.1.3)
$INST_TOP/apps/$CONTEXT_NAME/logs/ora/10.1.3/Apache/error_log[timestamp]
$INST_TOP/apps/$CONTEXT_NAME/logs/ora/10.1.3/opmn/ (OC4J~…, oa*, opmn.log)$INST_TOP/apps/$CONTEXT_NAME/logs/ora/10.1.2/network/ (listener log)
$INST_TOP/apps/$CONTEXT_NAME/logs/appl/conc/log (CM log files)
Log files related to cloning in R12
Preclone log files in source instance
 Database Tier - /$ORACLE_HOME/appsutil/log/$CONTEXT_NAME/(StageDBTier_MMDDHHMM.log)
 Application Tier - $INST_TOP/apps/$CONTEXT_NAME/admin/log/ (StageAppsTier_MMDDHHMM.log)
Clone log files in target instance
Database Tier - $ORACLE_HOME/appsutil/log/$CONTEXT_NAME/ApplyDBTier_.log
Apps Tier - $INST_TOP/apps/$CONTEXT_NAME/admin/log/ApplyAppsTier_.log

If your clone on DB Tier fails while running txkConfigDBOcm.pl (Check metalink note - 415020.1)
During clone step on DB Tier it prompts for “Target System base directory for source homes” and during this you have to give like /base_install_dir like ../../r12 and not oracle home like ../../r12/db/tech_st_10.2.0

Patching related log files in R12
 Application Tier adpatch log - $APPL_TOP/admin/$SID/log/
 Developer (Developer/Forms & Reports 10.1.2) Patch - $ORACLE_HOME/.patch_storage
 Web Server (Apache) patch - $IAS_ORACLE_HOME/.patch_storage
 Database Tier opatch log - $ORACLE_HOME/.patch_storage
Autoconfig related log files in R12
Database Tier Autoconfig log :
 $ORACLE_HOME/appsutil/log/$CONTEXT_NAME/MMDDHHMM/adconfig.log
 $ORACLE_HOME/appsutil/log/$CONTEXT_NAME/MMDDHHMM/NetServiceHandler.log
Application Tier Autoconfig log :
 $INST_TOP/apps/$CONTEXT_NAME/admin/log/$MMDDHHMM/adconfig.log
Autoconfig context file location in R12
 $INST_TOP/apps/$CONTEXT_NAME/appl/admin/$CONTEXT_NAME.xml
Other log files in R12
Database Tier
Relink Log files :
 $ORACLE_HOME/appsutil/log/$CONTEXT_NAME /MMDDHHMM/ make_$MMDDHHMM.log

Alert Log Files:
 $ORACLE_HOME/admin/$CONTEXT_NAME/bdump/alert_$SID.log
Network Logs:
 $ORACLE_HOME/network/admin/$SID.log
OUI Logs
OUI Inventory Logs :

 $ORACLE_HOME/admin/oui/$CONTEXT_NAME/oraInventory/logs
Application Tier
 $ORACLE_HOME/j2ee/DevSuite/log
 $ORACLE_HOME/opmn/logs
 $ORACLE_HOME/network/logs
Tech Stack Patch 10.1.3 (Web/HTTP Server)
 $IAS_ORACLE_HOME/j2ee/forms/logs
 $IAS_ORACLE_HOME/j2ee/oafm/logs
 $IAS_ORACLE_HOME/j2ee/oacore/logs
 $IAS_ORACLE_HOME/opmn/logs
 $IAS_ORACLE_HOME/network/log
 $INST_TOP/logs/ora/10.1.2
 $INST_TOP/logs/ora/10.1.3
 $INST_TOP/logs/appl/conc/log
 $INST_TOP/logs/appl/admin/log