There is one white papers from Oracle in area R12 Oracle Subledger Accounting. This was released sometime in last year Sept 2007, seems this is updated with latest version of April 2008.

• The Business Benefits of Oracle Subledger Accounting
  An Oracle White Paper
  September 2007 (latest version is of April 2008 )

Subledger & General Ledger
Those who are not having accounting background should understand , every accounting system will have a number of subsidiary ledgers (called subledgers) for items such as cash, accounts receivable, accounts payable, inventory , purchasing like wise. All the entries that are entered (called posted or booked) to these subledgers will transact through the general ledger account. For example, when a credit sale posted in the account receivable subledger turns into cash due to a payment, the transaction will be posted to the general ledger and the two (cash and accounts receivable) subledgers as well.
There are instances when items will go directly to the general ledger without any subledger.These items will be linked to your balance sheet but not to your profit and loss statement
The Concept is more or less addressed same in newly R12 SLA accounting , therefore you should note:

• A transactional application that generates accounting impact.
• Used to store detailed information not needed for a general ledger
• Subledgers post summarized activity to a general ledger periodically to maintain centralized account balances for the company