Concurrency (Magic xpa 3.x)
Concurrency is when at least two users are accessing the same application at the same time. This section focuses on how to allow concurrent users to access the same data without any loss of data. The following example illustrates the importance of data integrity in a concurrent work environment.
Two users are accessing a database table called Stock Level. Currently, there are 94 items in stock. The first user enters the Total in Stock column to update the item number to 93 (having sold an item). The second user enters the Total in Stock column to update the item number to 92 (having sold two items). Three items have been sold, but the number of items only reflect the sale of two items. Data was lost because of a lack of data integrity.
Locking Methods
Identify Modified Row
Transactions
Locking Strategy
Task Nesting and Locking
Isolation Level
Differential Update
