Example of Multiphase Coordination - Parallel Transporter

The following table shows a simplified example of using the multiphase coordination protocol with three instances of the Load operator running in a master-slave relationship. In this execution, the slave operators behave as if they are in an idle mode while the master operator establishes the processing environment. Independent parallel processing then begins when all operators reach the synchronization point.

Upon execution, the Teradata PT processor invokes each operator in the parallel execution plan using the Initiate, Execute, Checkpoint, Restart, or Terminate functions. In return, each operator returns its status with either a SamePhase, NextPhase, or EndMethod response.

Method processing continues in the first phase until each instance of the operator has returned a NextPhase status, which signifies the end of the first phase and the beginning of the second. This phase processing continues, with no limit to the number of phases allowed, until each instance of the operator has returned an EndMethod status.

The entire process repeats for each method, with the SamePhase, NextPhase, and EndMethod status returns providing the synchronization points for the multiphase coordination.

The multiphase coordination protocol is also available for operators that are not master/slave oriented. As indicated, the phase coordination process is implemented and controlled by the operators themselves, not by the Teradata PT processor. Under this protocol, operators are free to coordinate operations among themselves by using the appropriate status returns to guide the Teradata PT processor.

Using Multiphase Coordination Protocol
Method	Phase	Master Operator Object	Slave 1 Operator Object	Slave 2 Operator Object
Initiate	1	Allocate global variables	Create/connect a Teradata SQL session	Create/connect a Teradata SQL session
		Create/connect a Teradata SQL session for obtaining the LSN parcel	Return NextPhase	Return NextPhase
		Extract LSN from the LSN parcel
		Save LSN as a global variable
		Create/connect a Teradata SQL session
		Return NextPhase
	2	Create/connect Load sessions using the LSN global variable	Create/connect Load sessions using the LSN global variable	Create/connect Load sessions using the LSN global variable
	2	Return NextPhase	Return EndMethod	Return EndMethod
	3	Issue Begin Loading
	3	Return EndMethod
Execute	1	Read record from a data source	Read a record from a data source	Read a record from a data source
	1	IF end-of-file, return NextPhase ELSE return SamePhase	IF end-of-file, return EndMethod ELSE return SamePhase	IF end-of-file, return EndMethod ELSE return SamePhase
	2	Issue End Loading (if specified by the user)
	2	Return EndMethod
Checkpoint	1	Write statistics to Global Variable	Write statistics to Global Variable	Write statistics to Global Variable
	1	Return NextPhase	Return EndMethod	Return EndMethod
	2	Write checkpoint records to the restart log file
	2	Return EndMethod
Restart	1	Process checkpoint records	Process checkpoint records	Process checkpoint records
	1	Return NextPhase	Return EndMethod	Return EndMethod
	2	Write a restart record to the restart log file to indicate end-of-restart
	2	Return EndMethod
Terminate	1	Disconnect Load sessions	Disconnect Load sessions	Disconnect Load Sessions
	1	Return NextPhase	Return NextPhase	Return NextPhase
	2	Disconnect Teradata SQL session	Disconnect Teradata SQL session	Disconnect Teradata SQL session
		Deallocate Global Variables	Return EndMethod	Return EndMethod
		Return EndMethod	Return EndMethod	Return EndMethod