AM Pooling

Application Module Responsibilities

• Manage transaction against a data source
• Manage session's state

Root vs Nested vs Shared AMs

• Root AM
• Created for each user session
• Stored in the pool
• Handles transactions, connections, state
• Nested AM
• A logical construct only for grouping VOs
• Are themselves nested under a root AM
• Delegates all responsibilities to the root AM
• reference to a nested AM in the pool is really reference to it's parent
• Shared AM
• They are shared across all user sessions

Settings

• AppModule(AppModule.xml) -> Configurations -> 
• The settings are stored in bc4j.xcfg 

• Common Passivation Mistakes
• Variables in AppModuleImpl & ViewObjectImpl
• Override passivateState() and activateState()
• ADF BC VO transient attributes to be passivated if needed.

Application Module lifecycle

• AM statuses are Available, Unavailable or referenced
• Available - Ready for use
• Unavailable - Processing, currently checked out to a servlet thread
• Referenced - Processing complete, Checked into pool, Pinned for session future request
• Available - All AMs are initially marked available for use in the pool when instantiated
• Unavailable - Upon new request any available AM will be "checked out" for a servlet thread
•  

Passivation

• Offloads AM state to a persistent store -  maintained in table ps_txn in XML format
• Transactional data - new, modified and deleted entities
• Non-Transactional data 
• Current row indicator
• new rows and their position
• View Criteria and parameters
• Flag indicating whether the rowset had been executed 
• Range start and size
• Access mode
• Fetch mode and size
• Any view object custom data
• Transient view object attributes if configured
• Select, from, where and order by clauses if created dynamically
• Doesn't passivate
• Query rows - They are passivated only if modified, deleted or new row created
•  
• Alternate reasons for Passivation
• Fail over support
• Or jbo.ampool.doampooling=false
• For testing passivation by eagerly turning it on
• Or jbo.doconnectionpooling=true & jbo.txt.disconnect_level=0(but not 1)

 

Cleaning the Applicaiton Module pool

Passivation Mistakes

• Using member variables in AppModuleImpl or ViewObjectImpl
• Adf bc doesn't automatically passivate above member variables by default
• One need to override passivateState() & activateState() to ensure they are read and written
• View Object Transient attributes
• Explictly set VO transient attributes to be passivated if needed