Cannot edit a record in User to person relationship (DirPersonUser). Update on a valid time state table is not allowed without specifying a ValidTimeStateUpdateMode.

This table need update in validTimeStateUpdateMode field.

while you update the record you need to define [table].validTimeStateUpdateMode also.

sample code :

DirPersonUser           personusertable;

    ;

    

    select forUpdate personusertable

    where personusertable.RecId == 5637174578;

    ttsBegin;

        personusertable.PersonParty = 5637286583;

        personusertable.validTimeStateUpdateMode(ValidTimeStateUpdate::Correction);

        personusertable.update();

    ttsCommit;

https://hellodax.com/2015/06/25/error-update-is-not-allowed-without-specifying-validtimestateupdatemode/