Building on Gayathri's and Debroop's comments, for those that don't know this (it's not documented well/at all): The "Effort" task
- is created when one starts adding resources to the Staff page before creating any tasks on the WBS - CA PPM needs a task to build the resource hours from - if there aren't any, it creates one
- may be named "Effort" or after the project's name, depending on CA PPM version one is using
- has "~rmw" as task ID
- can be created manually by adding "~rmw" to a task
- can be disabled by modifying the task ID (e.g. remove "~" )
- can be avoided by creating tasks first, then adding staff
- Projects using the "Effort" task with "~rmw" were called "Fast Plans" back in the day (ABT days)
- Projects not using this, using normal WBS for planning effort and tracking actuals, were called "Power Plans"
When using a "Fast Plan," the Project's Allocation should equal the total ETC of the Effort Task - as the task with the ~rmw is the only task considered by a Fast Plan - it doesn't worry about the pesky details that one might add later with more tasks and assignments. Ignoring pesky details is "Fast." Working with the full WBS is powerful. Fast or powerful - both sound great, yes?
Once the ~rmw is removed, or if it was never there, one is dealing with a "Power Plan" - the Allocation is almost never equal to the ETC from all of the tasks, unless one purposely uses the "Allocate from Estimates" action on the Team\Staff Actions pull-down menu. The purpose for this is that one may allocate a resource 100% to the project, yet only have task assignments totally 50% for the resource (Allocation = 1000 hours; ETC = 500), allowing the project manager to hold the difference in reserve - project manager may know that the resource will be used, but has not yet identified which tasks the resource will be assigned to. If the project manager knows that the difference will not be used, the "Allocate from Estimates" action can be used, setting Allocation = ETC = 500, freeing the resource's unused allocation for use on other projects.
Please, checkout the link Tomomichi provided.
Hopefully, you find some value in my description of Fast/Power Plans.