Hi Paulo,
There is no external function available to initiate the repository synchronisation, however there are a couple of workarounds.
For RTDM v6.3 or less: the Batch Activator command line utility can be used to deactivate/activate a decision flow. When performing this action, the activator calls the synchronise repository method. So the workaround is to create a dummy campaign in the repository, and then use the Batch Activator to activate/deactivate it, thereby causing a repository synch.
For RTDM 6.4 or higher: the batch activator approach above is still valid, but there is also a REST API (Decision Services Administration) which does the same sorts of things as the CLI Batch Activator. So you can program a REST call (instead of a CLI utility) to do the activation instead.
Regards
James