When you launch the gantt chart for some projects, none of the project tasks are appearing in the chart (the chart is completely blank). When you try to filter for all tasks, you get a SQL error:
ORA-00001: unique constraint (schema.TEMP_WBS_GLOBAL_PK) violated
The gantt is unable to display tasks because there is more than one task with the same WBS sort value on this project.
To confirm that this is the case, the WBS Sort column can be configured on the Task List or the following query can be run in the database:
select i.code Project_Code, t.prwbssequence Dup_WBS_SORT, count(*)
from prtask t, inv_investments i
where t.prprojectid = i.id
group by i.code, t.prwbssequence
having count (*)>1
To reset the tasks WBS sort on the project tasks to where the sort value will be unique, there are three options:
Note: Check if the project has missing IDs for tasks
Reference: WBS Sort numbers are not unique