OObjectDatabaseTx db = new OObjectDatabaseTx ("remote:localhost/demo").open("admin", "admin");
db.getEntityManager().registerEntityClass(A.class);
db.getEntityManager().registerEntityClass(B.class);
db.begin();
try {
    int amt = 10;
    OCommandSQL cmd = new OCommandSQL("update A set id = eval('id - $id') where eval('id - $id') > 0");
    cmd.getContext().setVariable( "id", 100 );
    int recordsUpdated = db.command(cmd).execute();
    //int recordsUpdated = db.command(new OCommandSQL("update A set id = eval('id - "+ amt +"') where eval('id - "+ amt +"') > 0")).execute();
    B b = new B();
    b.setName("B class");
    db.save(b);
    System.out.println(recordsUpdated);
    throw new Exception();
} catch (Exception e) {
    System.out.println("rollbacked...");
    db.rollback();
}

/*OCommandSQL cmd = new OCommandSQL("update A set id = eval('id - $id') where eval('id - $id') > 0");
cmd.getContext().setVariable( "id", 100 );
int recordsUpdated = db.command(cmd).execute();*/
int recordsUpdated = db.command(new OCommandSQL("update A set id = eval('id - "+ amt +"') where eval('id - "+ amt +"') > 0")).execute();