There is a requirement of making the pri key field in a synchronized child session modifiable. This is possible by setting a variable 'modify.prim.key' to true. But session does not behave properly when i save the record after modifying the key field value. All fields get blank out and do not show the modified record. More details are attached in the doc file..

For obvious(or not) reasons change the prim key value is not recommended directly. You can face such problems as duplicate values and other issues that most appear if you are changing using the GUI.

On you situation i recommend you to make a function to handle that. When the primary key is changed you can save the old values, delete the current record and creates a new one using the new key. To solve the problem around the parent session, refers to refresh.parent() function.