Orphaned records after Project was deleted.
There are several related records that are Cascade Deleted when a Project record is deleted and several that are retained.
Out of the Box, we delete the following records when a Project is deleted:
Project Task, Project Task relationships/dependencies, Cost Plans, Cost Plan Breakdowns, Benefit Plans, Benefit Plan Breakdowns, Expense Lines, Status Reports, Risks, and Expense Lines.
We retain records from the following tables:
Any associated Story (rm_story), Requirement (dmn_requirement), Resource Plan (resource_plan) and any records that stem from it, Issue (issue), Decision (dmn_decision), Action (project_action), Project Change Request (project_change_request), Time Card (time_card).
We keep all Resource/Time related records to make sure we have a proper record of all time allocated to users and time worked.
It is typically recommended that you do not delete unneeded Project records but rather set them to an inactive state like "Cancelled".