Request monitor elements

Request monitor elements, also known as request metrics, measure the volume of work or effort expended by the database server to process different types of requests, including overall system processing, requests related to a specific type of processing, and requests related to a specific data server environment. Use request monitor elements to monitor the database system, specifically the volume of work and the effort expended by the data server to process application requests.
A request is a directive to a database agent to perform some work that expends database resources. Sources of the request can include:
  • A directive issued directly by an external application, such as an OPEN or EXECUTE directive. These are referred to as application requests.
  • A directive issued by a coordinator agent to a subagent at the same or a different database member.
  • A directive issued by an agent at a different database member.
Some representative monitor elements for measuring overall system processing information:
  • The rqsts_completed_total monitor element measures the number of completed by the system.
  • The total_rqst_time monitor element measures the time spent by requests in the data server, including wait time and processing time
  • The total_wait_time monitor element measures the overall wait time.
  • The total_cpu_time monitor element measures the CPU usage time.
Some representative monitor elements for measuring client-server processing information:
  • The client_idle_wait_time monitor element measures the time spent waiting for the next request from an open connection.
  • The tcpip_recv_volume monitor element measures the volume of data received by the data server from clients over TCP/IP.
Some representative monitor elements for measuring common data server processing operations:
  • pool_data_l_reads is one of the monitor elements providing information about buffer pool resource usage.
  • pool_read_time is one of the monitor elements providing information about I/O processing.
  • lock_wait_time is one of the monitor elements providing information about locks and locking.
  • total_section_sorts is one of the monitor elements providing information about sorts.
Some representative monitor elements for monitoring processing relevant to selected types of data server environments:
  • fcm_recv_wait_time is one of the monitor elements measuring fast communications manager (FCM) processing.
  • wlm_queue_time_total is one of the monitor elements measuring workload management control actions.

Accessing request metrics using table functions

You can use the following table functions to access the request metrics:
  • MON_GET_SERVICE_SUBCLASS and MON_GET_SERVICE_SUBCLASS_DETAILS
  • MON_GET_WORKLOAD and MON_GET_WORKLOAD_DETAILS
  • MON_GET_CONNECTION and MON_GET_CONNECTION_DETAILS
  • MON_GET_UNIT_OF_WORK and MON_GET_UNIT_OF_WORK_DETAILS
Each table function in this set of monitor table functions has two forms, one of which has a name ending with "DETAILS." The function that does not end with "DETAILS" provides an SQL relational interface that returns the most commonly needed data. The other function provides XML-based access to the monitor data and returns a more comprehensive set of data.

This set of table functions enables you to focus on request metrics at a particular level of aggregation. You can choose the table function that enables you to focus on subset (or aggregation) of the system workload you are interested in a given situation. All of these table functions include a common set of request metric monitor elements. Each table function may return a few additional details not common with all the table functions.

In a database with no user-defined workloads or service classes, all of the user work performed by the database manager occurs in the default user workload and user service class. The table functions that return data for each service class (or workload) return data for a single service class (or workload) that represents the processing for the user workload for the entire database.

In a database with user-defined workloads and service classes, table functions that return data for each service class (or workload) enable you to compare processing per service class (or workload). Using SQL, you can sum the values across service classes (or workloads) to obtain the value of a monitor element that represents the processing for the user workload for the entire database.

Accessing request metrics using event monitors

Request metrics are reported by the following event monitors:
  • Statistics event monitor - Request metrics are one of several types of information reported by this event monitor.
  • UoW event monitor - This event monitor reports similar or identical fields as the MON_GET_UNIT_OF_WORK table function