A car's ignition switch serves several purposes. First, it allows you to control the power to many of the car's accessories, preventing accessories from running down the car's battery when the car is parked for a long period of time.
Cardinality is the term used in database relations to denote the occurrences of data on either side of the relation. In the common data architecture, cardinality is documented with data integrity but not with data structure. There are several types of cardinality defining relationships between occurrences of entities on two sides of the line of relationships.
If 100-percent accuracy is required, database mirroring requires that the mirror server instance always stay current; in other words, the system must immediately copy every change in the principal's content to the mirror and vice-versa. In this mode, known as synchronous operation, the mirror is called a hot standby. While database mirroring can also work when the content is not fully synchronized, some data loss may occur if one of the server instances fails or becomes inaccessible.