An Apama query is a self-contained processing element that communicates with other queries, and with its environment, by sending and receiving events. Queries are designed to be multithreaded and to scale across machines.

You use Apama queries to find patterns within, or perform aggregations over, defined sets of events. For each pattern that is found, an associated block of procedural code is executed. Typically this results in one or more events being transmitted to other parts of the system.

A query is defined in a .qry file. A query finds specified event patterns or aggregates event values.

Apama queries are useful when you want to monitor incoming events that provide information updates about a very large set of real-world entities such as credit cards, bank accounts, or cell phones. Typically, you want to independently examine the set of events associated with each entity, that is, all events related to a particular credit card account, bank account, or cell phone. A query application operates on a huge number of independent sets with a relatively small number of events in each set.

The following topics provide reference information for the parts of a query definition. For user guide type information, see Defining Queries.