You're not the only one unable to compile it. The code is dependent on dbmanager.h and won't build without it, and dbmanager.h (and any library or other source code it relates to) is not referenced anywhere. Simply removing #include <dbmanager.h> WON'T solve the problem because there are references within the code, i.e.:
DbManager* dbm = NULL;
dbm = new DbManager(userName);
oras = dbm->getOracleServices();
Connection * conn = oras->connection();
dbm->rollbackActions(ex, stmt, resultSet);
OP: how about providing dbmanager.h and dbmanager.cpp, or at least stating where it can be found, so that people can actually use this example?