The organization information used in HR is as follows
1. Business Group
2. HR Organization
The HR organization classification used in oracle financials applications are as follows
1. GRE/Legal Entity
2. Operating unit
3. Company Cost Center(Used in financials DBI)
4. Auditable Unit(Used in ICM module)
5. Assets Organization (Used in Financial Payables : Assets)
To define Business group, LE, OU, Organization, HR Organization etc check out below link
http://oracleerpappsguide.blogspot.com/2012/01/organization-in-r12.html
SOB is a sepcial organization in multi-org model. Its a financial entity that shares a particular hart of account, finctional currency and finncial accounting calendar. A General Ledger (GL) secures transaction information bu SOB.
An SOB is the highest level that affects the accounting aspects of business. One BG can be associated with multiple SOBs, but one SOB can be associated with only one BG. Each SOB has 3Cs.
 

 
When you use GL, you need to choose a responsibility that specifies a particular SOB(with the profile – GL SET OF BOOKS NAME). This allows you to get information fo that SOB only. In Oracle applications, you can create an SOB using the set of books window in GL. In the set of books window, you can define all other types of organization using the organization window.
With the multi-Org enhancements, multiple SOBs can use the same global item master organization. This is because the item master organization is used for item definition and not for item accounting information. All accouting-related attributes in the item master are controlled at the item level or organization level.
A balancing entity is one for which you prepare a balance sheet as a balancing segment value in the Accounting Flexfield structure. In any OU, you can have multiple balancing entities and each of these must balance within itself.
In oracle applications, all intercompany entries are automatically created within the SOB to ensure that companies are never out of balance. A legal entity can have one or more than one balancing segments. For example, you may have multiple companies defined in your COA reporting to a single legal entity.
How to decide Legal Entities and OUs
There two things one should consider while creating legal entities
1. The number of fisical and tax report the organization has to produces – for each distinct values we should create one legal entity.
2. The number of entities for which the company produce balance sheet – for each distinct values we should create one legal entity.
An operating unit a is a fincial entity in a business group that engages in transactions with outsiders and for which you want to track the finalcial transactions.
OU deals with 5 subledgers – OM, AR, PO, AP and GL
Security and Subledgers decides how many operating units one should create in a business group.
Each company defined in your COA may have multiple divisions which you produc balance sheets. In that case, it is likely that each company in the COA is setup as a legal entity and each division is setup as an OU.
 
Securing values
Oracle Applications does not automatically secure balancing segment values within your COA with specific legal entities or OU. You can create security rules to ensure this security requirement. For example, you can ensure that the payables team may access invoices of a specific division. If security rules are not defiend, access to all divisions will be available.
 
To explain different balancing entities, assume that there is one GL SOB, balancing segment value is the company segment, and that there are three companies 10, 20 and 30. You should ensure that OUs are associated with responsibilities, and each responsibility is associated with one and only one OU. In the case the company 10 is a legal entity in which two divisions Div1 and Div2 are defined as OUs. You can create a security rule to ensure that when users log in with a particular responsibility, they should only be able to enter transactions with compnay 10, and the users from company 20 and copnmany 30 should not be allowed.
 
The Oracle Applications organization model defines organizations and the relationships among them in arbitrarily complex enterprises. This organization model serves as the cornerstone for all of the Oracle Applications products. It dictates how transactions flow through different organizations and how those organizations interact with each other.
Multi-Org is an application and database enhancement that enables multiple business units(operating units) in an enterprise to use a single installation of oracle applications products while keeping transaction data separate and secure.
Major Features of Multi-org
Multiple Organizations in a Single Installation
You can define multiple organizations and the relationships among them in a single installation of Oracle Applications. These organizations can be ledgers, business groups, legal entities, operating units, or inventory organizations.
Secure Access
You can assign operating units to a security profile and then assign the security profile to responsibilities or users. If multiple operating units are assigned to the security profile, then a user can access data for multiple operating units from a single
responsibility. This ensures that users can only access, process, and report on data for the operating units they have access to.
Data Security
You can limit users to information relevant to their organization. For example, you can limit access for order administration clerks to sales orders associated exclusively with their sales office.
Inventory Organization Security by Responsibility
You can specify the inventory organizations that are available to users in each responsibility. The Choose Inventory Organization window automatically limits available inventory organizations to those authorized for the current responsibility.
Responsibility Determines Operating Unit
Your responsibility determines which operating units you can access when you use Oracle Applications. If you only want a responsibility to access only one operating unit, then set the profile option called MO: Operating Unit. If you want a responsibility to access multiple operating units, then define a security profile with multiple operating units assigned and assign it to the MO: Security Profile profile option. Additionally, if using the MO: Security Profile profile option, you can also set the MO: Default Operating Unit profile option to specify a default operating unit that will default in transaction entry pages.
Types of Organizations
You can define organizations and the relationships among them. You can define security for either an organization hierarchy or list of organizations.
Business Group
The business group represents the highest level in the organization structure, such as the consolidated enterprise, a major division, or an operation company. The business group secures human resources information. For example, when you request a list of employees, you see all employees assigned to the business group of which your organization is a part.
The business group drives the legislation used for human resources and payroll purposes. If the implementation involves employees in multiple countries, then it will likely require several different business groups, one for each country where employees are located. This assumes that the company does not seek to customize multiple legislative requirements into one business group.

The HRMS best practice recommends that a new business group should represent a country or regional level partition of data. All companies that operate in the country or regions should be represented as legal employers in the business group.

SOB/PL
Set of books in 11i consists of 3Cs – Chart of Account, calendar, currency
Primary ledger in R12 consists of 4Cs
See the child chapter to this
http://www.oracleug.com/user-guide/basics-oracle/define-sob
Legal Entity


A legal company for which you prepare fiscal or tax reports. You assign tax identifiers and other legal entity information to this type of organization.
You can define legal entities using Legal Entity Configurator or Accounting Setup Manager in General Ledger.

 


Operating Unit

  • An organization that uses Oracle subledgers, such as Oracle Cash Management, Order Management and Shipping Execution, Oracle Payables, Oracle Purchasing, Oracle Receivables, and related products. It may be a sales office, a division, or a department.
  • In R 12 Operating units are not associated with legal entities. Operating units are assigned to ledgers and a default legal context.
  • Information is secured by operating unit for these applications using responsibilities. Each user can access, process, and report on data only for the operating units assigned to the MO: Operating Unit or MO: Security Profile profile option. The MO: Operating Unit profile option only provides access to one operating unit. The MO: Security Profile provides access to multiple operating units from a single responsibility
  • You can define operating units from the Define Organization window in Oracle HRMS or from Accounting Setup Manager in General Ledger.
Inventory Organization
  • An organization for which you track inventory transactions and balances, and/or an organization that manufactures or distributes products. Examples include (but are not limited to) manufacturing plants, warehouses, distribution centers, and sales offices.
  • The following applications secure information by inventory organization: Oracle Inventory, Bills of Material, Engineering, Work in Process, Master Scheduling/MRP, Capacity, and Purchasing receiving functions. To run any of these applications, you must choose an organization that has been classified as an inventory organization.
  • You can create ledgers using the Accounting Setup Manager in Oracle General Ledger and define organizations using the Define Organization window.
HR Organization
HR organizations represent the basic work structure of any enterprise. They usually  represent the functional management, or reporting groups that exist within a business group. In addition to these internal organizations, you can define other organizations for tax and government reporting purposes, or for third party payments.
Information Shared Across Organizations
The following information is global. It must be set up once for the enterprise:
• Flexfield definitions
• Customer Header (customer site is at the operating unit level)
• Supplier Header (supplier site is at the operating unit level)
Adding a New Operating Unit
The following steps are required to add new operating units to your organizational structure:
1.1 Revise the Organization Structure.
1.2 Define Sets of Books (optional).
1.3 Define Locations.
1.4. Define Organizations and Relationships.
2.1 Define Responsibilities.
2.2 Set Profile Options for Each Responsibility linked to the new Operating Unit.
1.1. HR: Business Group
1.2  HR: Security Option
1.3: HR: User Type (FOR accessing HRMS functions)
1.4  HR: Cross Business Group
2.1. GL: Set of Books(11i)
2.1  GL:%Ledger%  (R12)
2.3  GL: Data Access Set. This profile option to control the ledgers that can be used by Oracle General Ledger.
3.1. MO: Operating Unit
3.2. MO: Security Profile (R12)
3.3. MO: Default Operating Unit
4.1 Tax: Allow Override of Tax Code
4.2 Tax: Invoice Freight as Revenue
4.3 Tax: Inventory Item for Freight
5.1 Sequential Numbering
5.2 INV: Intercompany Currency Conversion
2.3 Run the Replicate Seed Data concurrent program.
3.1 Define Inventory Organization Security.
3.2 Define Intercompany Relations (optional).
3.3 Implement the Application Products.
4.1 Secure Balancing Segment Values (optional).
4.2 Run the Setup Validation Report (recommended).
4.3 Implement Document Sequencing (optional).
4.4 Set the top reporting level (optional).
4.5 Set up conflict domains (optional).