I do not seem to get - what I think should be the default behavior - working with a PK on a FMemTable. I am using Delphi 10 Seattle. As an example I define one new field in the FDMemtable, set a PK index, add a DBnavigator, a DBGrid and a DataSource - classic Delphi 1 example. Now entering data in the table and posting - I can add multiple rows with similar values. I would have expected a key-viol to be raise on my post on the second record - but first when I do a refresh - I get the expected behavoir. Some of the other properties on the FDMemtable like Required is also ignored on the post. Well I was actually surprised also to see this on a ClientDataset - I am probably getting old - but a post should validate the constrains - right.