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The following page has been changed by KevinWilliams:
http://wiki.apache.org/ws/Tuscany/TuscanyJava/DAS_Java_Overview/RDBDAS_Java_User_Guide/OCC

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  The RDB DAS is intended for use in disconnected scenarios.  When the DAS 
returns a graph of SDO !DataObjects as the result of a query, there are no 
locks held on the  underlying database and the data is no longer associated 
with any database connection or transaction.  However, although locks are not 
held, the DAS does employ a mechanism called 
[http://en.wikipedia.org/wiki/Optimistic_locking Optimistic Concurrency 
Control] (OCC) to manage concurrency.
  
- Basically, when OCC is being utilized, the DAS checks whether the state of 
the database has changed since the original data was read before applying any 
writes to the same location.  For example, suppose that a DAS client reads a 
set of Customers, modifys one and then attempts to write the change back to the 
database:
+ Basically, when OCC is being utilized, the DAS checks whether the state of 
the database has changed since the original data was read before applying any 
writes to the same location.  For example, suppose that a DAS client reads a 
set of Customers, modifies one Customer and then attempts to write the change 
back to the database:
  
  {{{
     Command select = das.createCommand("Select * from CUSTOMER where LASTNAME 
= 'Williams'");

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