[otrs] config file location?

Hi, I hope this is not a stupid question. I am trying to optimise our OTRS installation, and I want to change the TicketIndexModule type from 'RuntimeDB' to 'StaticDB'. In which config file am I supposed to make this setting? I have added a line to the bottom of the "Load" subroutine in the Kernel/Config.pm file, but I have no way to verify if these have taken effect? I know about the Admin/SysConfig module, and from there if I search for TicketIndexModule, I get *nothing*. It seems I need to search for Ticket::IndexModule and then I can change the value, but where is this value stored, and can I see it and modify it manually? Thanks.