>My exact code when clicking a button for saving is this:
>
>

>SELECT rvCustomer
>lUpdate = TABLEUPDATE()
>IF lUpdate
>    REQUERY('rvCustomer')
>ELSE
>    MESSAGEBOX('Update failure',64,'update')
>ENDIF
>Thisform.Refresh()
>

>
>It does not trigger error as if no error at all but it goes to the messagebox. My database however was upsized from native VFP using upsizing wizard.

Read the docs for TABLEUPDATE(). If it returns .F., it fills AERROR() with information about why it failed.