What does ‘\l .’ or ‘system “l .”‘ do?

Typically, it’s used to reinitialize and alert an existing kdb process of a new partition. Note that command triggers the execution of any q scripts existing in the current working directory of the running kdb process.

This command allows kdb to continue running and servicing requests while a new partition is constructed. Running kdb remains unware of the new partition until the \l . command is issued.

See also: .Q.l