COMMITMENT CONTROL IN ADVANTAGE PLEX for DB2/400
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Transcript of COMMITMENT CONTROL IN ADVANTAGE PLEX for DB2/400
COMMITMENT CONTROL IN ADVANTAGE PLEX for
DB2/400
Yolanda Scholtz18 November 2002
Session - 4E
15:15 - 16:00
EDGE EMEA Conference - 2002
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Agenda
• Overview • Setting Up Commitment Control for DB2/400• Across Advantage Plex and Advantage 2E• Switching Commitment Control On or Off • Considerations• Commitment Control Errors• Additional Notes• Questions
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• Operations to run optimally
• Reliable data within Information Systems
• Improving / ensuring data integrity
• Reduce time spent on correcting data
Need & Benefits
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• Commitment Control is a database facility that enables a group of database changes to be treated as a single transaction, regardless of the files being changed.
Thus you can ensure that either ALL or NONE of the changes are performed.
Definition
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IllustrationParent
Child 1 Child 2
Calls
Updates
Updates Updates
ERROR
CommitChanges
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IllustrationParent
Child 1 Child 2
Calls
Updates
Updates UpdatesRollbackOccurred
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Setting up Commitment Control
Parent
Commit / Rollback
Child 1
Child 2
Child 3
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• Setting Up Commitment Control for DB2/400– Framework– Implementation
• Logic in the Patterns
• Commitment Control Functions
• Inheritance
• Development Standards
• Business Functions
Setting up Commitment Control
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Framework
• Commit Group– Parent– Child– None
• Commit / Rollback
• Journal OS/400 Physical Files
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• A Commit Group is a group of one or more data access functions within which all database changes are treated as a single transaction.
• Define a commit group using the triple
FNC Commit SYS verb
None Parent Child
Commit Group
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FNC Commit SYS None
None is the default value if no commit property is specified. It means that the function will not be part of a commit group.
Commit groups should be specified only where they are necessary, otherwise they serve only to decrease the performance of the function.
None
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FNC Commit SYS Parent
This server function belongs to a commit group and will be generated with the code that starts commitment control (unless another parent in the commit group has already started it).
A Commit group must have at lease one parent.
Parent
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FNC Commit SYS Child
This server function belongs to a commit group.
A commit group can have one, many, or no child functions.
Child
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• Commit and Rollback statements in action diagram – If not, the results will be unpredictable - any
database changes will remain uncommitted until another program executes a commit or rollback operation.
Commit / Rollback
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• Ensure that the OS/400 physical files being updated are being journalled.
• For information on journal management, refer to the AS/400 Advanced Backup and Recovery Guide.
Journal Physical Files
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• Pattern– Function Shell
• Functions– Commit Start– Commit End
• Inheritance
• Business functions
Implementation
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• Function Shell changes :– Local Variable and fields
• Commitment– Control Status– Control On
– Meta coding to interrogate triples of functions to determine if Commitment Control is required
– Initialise– Terminate
• Go SubCommit
– Additional Subroutine(Commit)– Rollback message
Pattern
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FunctionShell
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FunctionShell
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FunctionShell
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Purpose:
To ensure that STRCMTCTL command is executed (this is done automatically due to triple commit SYS parent)
Coding:
None
Commit Start
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Commit Start
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• Purpose:
– To ensure that ENDCMTCTL command is executed (this is done automatically due to triple commit SYS parent)
– To execute COMIT / ROLLBACK statement. (This is done exclusively in program)
Commit End
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Commit End
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• The FunctionShell is inherited by ALL functions
• Commit function inherits from main function
• Data Access function Commit - – auto created in model through inheritance– scoped to data access function
Inheritance
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• Naming Convention– MyEntity.MyFunction Commit
• Syntax• Model Editor
• Action Diagram
Development Standards
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Model Editor
MyFunction comprises MyFunction Commit
MyFunction Commit is a MyFunction
MyFunction Commit Commit Sys Child
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Action Diagram
Condition calls to functions
Coding may be copied to the desired place in the action diagram where a function call is done.
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• BENEFITS of Common Sequence– Remove monotony of coding the conditional
call construct– Eliminate errors in coding the conditional call
construct– To ensure standardization
Development Standards
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• Process Group– Set returning status (as it is always normal)
• Control Commit / Rollback – via Commit Subroutine– Commit Subroutine always in Terminate
Action Diagram
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• Either function (Plex or 2E) may contain the main commit point
• Both Plex and 2E functions may be specified as Child/Slave within the same Commit Group
• Only one Parent/Master may be defined
Across Advantage Plex and 2E
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Across Advantage Plex and 2E
Advantage Plex Advantage 2ECommit control option None None
Parent MasterChild Slave
Function / Command Commit / Rollback Commit
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As easy as
1... Set Triple COMMIT SYS (parent / none)
2... Gen & Build this main function
3... Start / End Journalling on affected
OS/400 files
On / Off Switch
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• Performance
• Replace default data access functions– In EDITDETAIL, EDITDIALOG, ect.
• Make function a Parent or Child
• Undefine the deleterow
• Replace with conditional coding
Reason: the default deleterow is automatically called in these functions (inheritance).
Considerations
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• If Client is parent– set Panel Properties<Window Type>=dialog
• to prevent another MDI child being executed simultaneously
– test returned status and set returning status• To ensure that rollback occurs if data access fails
– Call Commit Start in initialization section• STRCMTCTL auto executed if server parent
– Call Commit End for Commit / Rollback• auto executed if server parent
Considerations
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• Implementation timing– During vs After Development
• Identification of Business Functions
• Journal OS/400 Physical Files
• Development effort
• Test entire system
• Room for Error
• Impact on system maintenance and support
• Model Administration
• Integration impact
Considerations
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• unexpected Return Code = 01217.– Member EntityPF not journaled to journal *N
• Function check. CPF8351 unmonitored by FTN0001S at statement 845, instruction X'0179’.– Commitment control already active.
Commitment Control Errors
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• Can retrieve data from file during process• Can update same record twice• Cannot make changes to record externally• Terminate only executed on close• Commit desired business function, row or grid
• Files may be journalled and updated by functions NOT under commitment control
• If the function is under commitment control the files being referenced for update MUST be journalled
Additional Notes
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Questions
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Questions