Workflows expressed in Oozie can contain:
Oozie workflow is a collection of actions (i.e. Hadoop Map/Reduce jobs, Pig jobs) arranged in a control dependency DAG (Direct Acyclic Graph), specifying a sequence of actions execution. This graph is specified in hPDL (a XML Process Definition Language).
hPDL is a fairly compact language, using a limited amount of flow control and action nodes. Control nodes define the flow of execution and include beginning and end of a workflow (start, end and fail nodes) and mechanisms to control the workflow execution path ( decision, fork and join nodes).
Currently running workflow instances, including instance states and variables
Note: Oozie is a Java Web-Application that runs in a Java servlet-container - Tomcat and uses a database to store: