In this Document
  Purpose
  Scope and Application
  11g Install : Understanding about Oracle Base, Oracle Home and Oracle Central/Global Inventory locations
  References

Applies to:

Purpose

Scope and Application

11g Install : Understanding about Oracle Base, Oracle Home and Oracle Central/Global Inventory locations

Oracle Base :

For 11gR1, the ORACLE_BASE environment variable is only "recommended" but not "mandatory"; however for 11gR2 it is "mandatory".

The Oracle Base directory is the top-level directory for Oracle products installed by the same user.

During installation,
    - OUI gives an option to chose Oracle Base location (through drop down list box)
       or
    - we can create the Oracle Base directory and set the $ORACLE_BASE in the environment
       # mkdir -p /mount_point/app
       # chown -R oracle:oinstall /mount_point/app
       # chmod -R 775 /mount_point/app/

On UNIX systems, the Optimal Flexible Architecture (OFA) Naming syntax for Oracle base directory is  similar to the following:
           Syntax : /u[01-09]/app/
            Ex: "/u01/app/oracle" is an Oracle base directory created for the "oracle" user

Default Oracle Base location (displayed by OUI during installation) is based on:

• First time 11g installation:

1. ORACLE_BASE variable set in the environment 
2. If OFA-compliant path ( /u[01-09]/app/ ) exists and writable by ""
       Ex: /u01/app/oracle
   The first existing and writable directory from /u01 through /u09 will be used as the default, and an app/ directory will be created underneath it.   
3. Neither $ORACLE_BASE is set nor OFA-compliant path exists , then Oracle Base defaults to:
    "/app/"
    Ex: /home/oracle/app/oracle

• If it is not first time 11g installation, then OUI prefill drop down in the order of:

1. ORACLE_BASE set in the environment,
2. the Oracle Base from the inventory that is owned by this user
3. all Oracle Bases from the inventory that are owned by other users

In 11g, RDBMS diagnostic data (trace, alert logs) has been reorganized and is stored inside a common directory structure, the Automatic Diagnostic Repository (ADR). The location of the ADR (adr_base) is controlled by the Oracle "diagnostic_dest" parameter. Parameters background_dump_dest, core_dump_dest, user_dump_dest (in previous releases) are now deprecated and replaced by a single parameter  "diagnostic_dest" in 11g.

The default location for the ADR base will be tied to the $ORACLE_BASE environment variable.  If "diagnostic_dest" is set in the spfile, then its value will be treated as ADR base. Otherwise, ADR Base will be set to Oracle Base location.

An ADR home (adr_home) is a common directory structure that is used for storing trace files, alert logs, core files, and incident information (instance specific). An is always located under an . Address of an is: /diag/rdbms//.

   Ex : /diag/rdbms/ORCL/inst1

Oracle Central/Global Inventory

 In general, each Oracle installation contains two inventory locations
Central/Global Inventory: Directory containing info relating to all Oracle Products installed on a host. This location can be identified by Central inventory pointer (default inventory pointer) file i.e oraInst.loc in its standard location (i.e /etc or /var/opt/oracle in some UNIX flavours). Central inventory consists of a file called inventory.xml, which contains the list of OracleHome's registered/associated with this Central Inventory. User can chose the Central/Global Inventory location at the time of first oracle product installation on a host.
Local Inventory: Local inventory resides inside the 'inventory' subdirectory within each ORACLE_HOME and contain details about oracle software components installed in the Oracle Home. Local inventory contains, among other things, a file called comps.xml, which contains all the components as well as patchsets or interim patches installed in the ORACLE_HOME. Local inventory location is fixed and always resides in $ORACLE_HOME/inventory.

In this section, we are discussing about Central/Global inventory (but not Local inventory) location.

In 11g, Default Oracle Central/Global Inventory location (displayed by OUI during installation) is based on:

• If ORACLE_BASE (/u01/app/oracle) is set in the environment, then Oracle Central Inventory location displayed by OUI is:
  
       "$ORACLE_BASE/../oraInventory"  (/u01/app/oraInventory)

• If not, OUI uses OFA syntax as Default Location for Oracle Central Inventory Directory.

Oracle Universal Installer checks to see if you have created an OFA-compliant path in the format u[01-09]/app, such as /u01/app, and that the user running the installation has permissions to write to that path. If this is true, then Oracle Universal Installer creates the Oracle Central Inventory directory in the path /u[01-09]/app/oraInventory.

Ex: /u01/app/oraInventory

If user doesn't have writing permissions to create folder /u[01-09]/app/oraInventory then OUI errors with OUI-10033 OUI-10035.

• If  OFA-compliant path not exists and $ORACLE_BASE is not set,  then the Oracle Central Inventory directory is placed in the home directory of the user that is performing the installation.

Ex: /home/oracle/oraInventory   (/home/oracle is home directory for "oracle" user)

• If it is not the first time 11g installation, then OUI will use the existing Oracle Central Inventory created for the user

Oracle Home

• Oracle Universal Installer prompts to specify the path for Oracle Home directory. The default location for Oracle Home (displayed by OUI) is also depends on Oracle Base.
     Ex: /product/11.1.0/db_1
  It also sets the correct owner, group, and permissions on it. We do not need to create this directory.
  

References