Waste metal. Electromagnets can be used to separate magnetic materials such as iron and steel from mixed piles of trash. The metals are pulled out by the magnet while nonmagnetic objects such as glass and plastic stay behind.aste metal. Electromagnets can be used to separate magnetic materials such as iron and steel from mixed piles of trash. The metals are pulled out by the magnet while nonmagnetic objects such as glass and plastic stay behind.
The definition of pessimistic is constantly expecting the worst. An example of pessimistic is a person who always believes that something is going to fail. of or characterized by pessimism; expecting the worst.
Optimistic needs a three-tier architectures where you do not necessarily maintain a connection to the database for your session whereas Pessimistic Locking is when you lock the record for your exclusive use until you have finished with it. It has much better integrity than optimistic locking but requires you to be careful with your application design to avoid Deadlocks.