Release It!, 2nd Edition

Defining Stability

To talk about stability, we need to define some terms. A transaction is an abstract unit of work processed by the system. This is not the same as a database transaction. A single unit of work might encompass many database transactions. In an e-commerce site, for example, one common type of transaction is “customer places order.” This transaction spans several pages, often including external integrations such as credit card verification. Transactions are the reason that the system exists. A single system can process just one type of transaction, making it a dedicated system. A mixed workload is a combination of different transaction types processed by a system.

The word system means the complete, interdependent set of hardware, ...