Just to get an idea of the ballpark capabilities associated with transaction processing, let's look at the benchmark TPC-C, which has been designed by the Transaction Processing Performance Council to compare TP systems. It defines a (scalable) database and a workload designed to exercise the TP system. The results of running the benchmark are measured in "transactions per minute" (tpm). They also measure the cost of TP systems: they divide the five year purchase price plus maintenance, by the tpm rating, to give a dollar per transaction per second.
TPC-C is an order entry application and combines interactive and batch transactions, queued transactions, and aborted transactions. The sample TPC-C database is centered on the warehouse. The size of the database is proportional to the number of warehouses: each warehouse contributes the same rows. These include a warehouse record, 10 District records (geographic information), 30 000 customer, history, and order records, 9 000 new order records, 100 000 stock and order items and 300 000 order line items. These rows vary from eight bytes for each new order entry to 655 bytes for the customer entries. The transactions processed include new order, order status, delivery, payments, and stock level. These transactions use a combination of queries and updates.
For example, the stock level transaction determines the stocking for a district. The input to the query is a threshold, the output is all items that have been ordered recently whose stock level is below the threshold. It is processed as a query that: