Some Commonly Used COM+ Services

COM+ Services are a set of services commonly used by line-of-business applications. The services extend the capabilities of components and increase code reuse by supporting common application requirements and reducing the amount of code that developers must include in each component. The following services are among the most commonly used.

Automatic Transactions

Transactions are a system by which separate database operations are grouped together to guarantee the integrity of the underlying data. As an example, the process of transferring money from one bank account to another consists of two database updates—a debit from one account and a credit to another—which must succeed or fail as a unit. If the debit succeeds while the credit fails, money is destroyed, which tends to make customers unhappy. Conversely, if the credit succeeds while the debit fails, money is created, which definitely makes banks unhappy.

From the developer’s perspective, the COM+ Transaction Service allows components to appear to be directly updating one or more databases, when in fact the service is intervening to coordinate those updates with other components and other databases in the transaction, and enforcing the four key characteristics of transactions (sometimes dubbed “ACID” for their initial letters):