Thursday, May 5, 2011

Sequence Container in SSIS - Different ways of using Sequence Containers

Integration Services includes the Sequence container, which makes it simple to divide the control flow in a package into groups of tasks and containers that you can manage as a unit.
Using Sequence containers lets you handle the control flow in a package in more detail, without having to manage individual tasks and containers.
If a package has many tasks, it can be helpful to group the tasks in Sequence containers.

I'll explain different scenarios where Sequence Container paly an important role to implement business rules.

Scenario 1:
  • Sequence Task SC1 must execute first. SC1 may have many task with or without precedence constraints. The group of these task must execute prior to any other tasks in the package.
  • Sequence Task SC2 must start after completion of SC1. SC2 must execute irrespective of Failure/Success of SC1.
  • Sequence Task SC3 contains Maintenence Plan Tasks and should be followed by SC2. SC3 must execute only after successfully execution of SC2. 

Scenario 2:

  • Sequence Task SC1 must execute first.
  • Sequence Task SC2 must start based on logical condition. This condition can be based on package variables. 
  • Sequence Task SC3 contains Maintenence Plan Tasks and should be followed by both SC1 and SC2. SC3 must execute after successfully execution of SC1. SC3 should execute regardless of SC2 but if SC2 executes, SC3 must execute after SC2.

  Scenario 3: This is real scenario in many BI applications.

  • SC1 must execute prior to other task. This Sequence Container may contain many tasks to pull data from hetrogenious data sources.
  • SC2 should be followed by SC1. This can be used to Insert/Update dimension tables and fact tables along with intermediate tables (if any). This container may further contain Sub - Sequence Containers e.g. SC2(a) to handle dimension Insert/Update and SC2(b) to update Intermediate and Fact tables.
  • SC3 should be followed by SC2. This may contains SSAS Tasks to Build/Prcoess Cubes. This container may also have Sub - Sequence Containers e.g. SC3(a) to check whether Current Month partition exists or not. If Yes than Do Nothing Else Create Current Month Partitions using Script task. SC3(b) can be used to Process Dimensions and Current Month Partitions.
  • SC4 can be used for Maintenence Plan tasks. If SC3 successfully completed (Evolution operation - Expression and Constraint) than take Backup of Cube, Shrink Datamart and Take Backup of Datamart.
  • SC5 can be used for Recovery Paln. If SC3 fails, Restore Cube from previos & Latest Backup available..


However, there are many more ways of utilizing Sequence Containers. Further, things depends on complexity of business requirement rules defined.

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