After assignments have been performed, some symbols live in the DataSHIELD R session on the server side.
dsListSymbols(conn)An object that inherits from DSConnection-class.
Other DSConnection generics: 
DSConnection-class,
dsAggregate(),
dsAssignExpr(),
dsAssignResource(),
dsAssignTable(),
dsDisconnect(),
dsGetInfo(),
dsHasResource(),
dsHasTable(),
dsIsAsync(),
dsKeepAlive(),
dsListMethods(),
dsListPackages(),
dsListProfiles(),
dsListResources(),
dsListTables(),
dsListWorkspaces(),
dsRestoreWorkspace(),
dsRmSymbol(),
dsRmWorkspace(),
dsSaveWorkspace()
if (FALSE) {
con <- dsConnect(DSOpal::Opal(), "server1",
  username = "dsuser", password = "password", url = "https://opal-demo.obiba.org")
dsAssignTable(con, "D", "test.CNSIM")
dsListSymbols(con)
dsDisconnect(con)
}