You can use the stopsync subcommand to stop synchronization from the command line.
To stop synchronization, open a terminal window (or a Command Window) and type the idsync stopsync command as follows:
idsync stopsync [-D bind-DN] -w bind-password | - [-h Configuration Directory-hostname] [-p Configuration Directory-port-no] [-s rootsuffix] -q configuration_password [-Z] [-P cert-db-path] [-m secmod-db-path]
idsync stopsync -w admin password -q configuration_password
For detailed information about the stopsync arguments, review Common Arguments to the Idsync Subcommands.