According to locals I know and trust the service charge can be anything the restaurant wants it to be. Sometimes shared, usually not. If you want your tip to go to your server hand them cash separate from paying the tab. Even when I use a credit card to pay for dinner I give cash to the server. It will be appreciated. Tourists from certain countries tip nothing as that's the way it works for them at home where servers are paid a livable wage. I've always found it hard to believe those tourists don't know tips are what help feed the families of the bartenders, servers, housekeepers, etc..