database services








Database services are logical abstractions for managing workloads in Oracle Database. Services divide workloads into mutually disjoint groupings. Each service represents a workload with common attributes, service-level thresholds, and priorities. The grouping is based on attributes of work that might include the application function to be used, the priority of execution for the application function, the job class to be managed, or the data range used in the application function or job class. For example, the Oracle E-Business suite defines a service for each responsibility, such as general ledger, accounts receivable, order entry, and so on. Each database service has a unique name.
Connection requests can include a database service name. If no service name is included and the Net Services file listener.ora designates a default service, the connection uses the default service.
Services are built into the Oracle Database, providing a single system image for workloads, prioritization for workloads, performance measures for real transactions, and alerts and actions when performance goals are violated. Services enable you to configure a workload, administer it, enable and disable it, and measure the workload as a single entity. You can do this using standard tools such as the Database Configuration Assistant (DBCA), Net Configuration Assistant (NetCA), and Enterprise Manager (EM). Enterprise Manager supports viewing and operating services as a whole, with drill down to the instance-level when needed.
In Real Application Clusters (RAC), a service can span one or more instances and facilitate real workload balancing based on real transaction performance. This provides end-to-end unattended recovery, rolling changes by workload, and full location transparency. RAC also enables you to manage a number of service features with Enterprise Manager, the DBCA, and the Server Control utility (SRVCTL).
Services also offer an extra dimension in performance tuning. Tuning by "service and SQL" can replace tuning by "session and SQL" in the majority of systems where all sessions are anonymous and shared. With services, workloads are visible and measurable. Resource consumption and waits are attributable by application. Additionally, resources assigned to services can be augmented when loads increase or decrease. This dynamic resource allocation enables a cost-effective solution for meeting demands as they occur. For example, services are measured automatically and the performance is compared to service-level thresholds. Performance violations are reported to Enterprise Manager, enabling the execution of automatic or scheduled solutions.
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