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# Deployments-->EJB --> Monitoring--> Message-Driven EJBs

Run-time Statistics for MDBs Raw Monitoring Data for Message-Driven EJBs Tasks Related Topics

## Overview

This page displays run-time statistics for MDBs in the currently selected archive. You can display statistics for one or more server instances on which the EJB is deployed. The statistics are defined in Message Driven EJB Run-Time Statistics.

You can tailor this console page to display some or all of the underlying counts from which the statistics are calculated, by clicking Customize this View, and selecting the desired data from the list of available columns. The available data is defined in Raw Monitoring Data for Message-Driven EJBs.

The statistics and underlying counts reflect activity since the bean was last deployed.

## Run-time Statistics for MDBs

The following table defines the run-time statistics displayed for message-driven EJBs.

Table 90-1

Pool Miss Ratio | The pool miss ratio is a ratio of the number of times a request was made to get a bean from the pool when no beans were available, to the total number of requests for a bean made to the pool. The consequence of a pool miss is different for different types of beans. A pool miss for a stateless session bean will cause the requesting thread to wait for a bean to become available in the pool. The maximum time a thread will wait is equal to the transaction timeout value for the bean. Entity beans and message-driven beans will never wait for an instance to become available. Instead, a pool miss will cause the pool to create a new bean instance to service the request. Pool misses come at a cost since the executing thread will either have to wait for a bean to become available or have to wait for a new bean to be created. As such, it is best to try to keep your pool miss ratio to a minimum. For information on what to tune in response to the pool miss ratio statistic, see Pool Miss Ratio in the WebLogic Server Performance and Tuning Guide.
Destroyed Bean Ratio | The destroyed bean ratio is a ratio of the number of beans destroyed to the total number of requests for a bean. The EJB specification mandates that the EJB container destroys a bean when non-application exceptions are thrown from the bean during execution. Destroying beans comes at a cost, however, because destroyed beans will likely have to be replaced with new bean instances. As a result, you should keep your destroyed bean ratio to a minimum. For information on what to tune in response to the destroyed bean ratio statistic, see Destroyed Bean Ratio in the WebLogic Server Performance and Tuning Guide
JMS Connection Alive | Reports whether the EJB container has successfully connected to the JMS destination source and that therefore the message-driven bean is receiving messages. If this field's value displays as `false`, check the server log for possible reasons for connection failure.
Transaction Rollback Ratio | The transaction rollback ratio is the ratio of transactions that have rolled back to the number of total transactions involving the EJB. This information is useful for several reasons. First, it may be useful for signaling a problem with an application. For example, an unexpectedly high rollback ratio may be caused by a problem with a resource used by the application. It may also be useful in gauging the efficiency of an application. A high transaction rollback ratio may mean that a lot of work is being done only to eventually be rolled back, which is inefficient. For information on what to tune in response to the transaction rollback ratio statistic, see Transaction Rollback Ratio in the WebLogic Server Performance and Tuning Guide.
Transaction Timeout Ratio | The transaction timeout ratio is the ratio of transactions that have timed out to the total number of transactions involving an EJB. Timeouts can be especially concerning because they are a signal of inefficiency. Every EJB request uses valuable server resources such as threads and bean instances. A timed out transaction means that server resources were tied up in vein. The transaction timeout ratio is a good indicator of a problem with an application. For information on what to tune in response to the transaction timeout ratio statistic, see Transaction Timeout Ratio in the WebLogic Server Performance and Tuning Guide.

Message Driven EJB Run-Time Statistics

## Raw Monitoring Data for Message-Driven EJBs

This section defines the underlying run-time counts from which the statistics in Run-time Statistics for MDBs are calculated. To display the counts on the EJB --> Monitoring --> Message Driven EJBs tab page, select "Customize this View" and choose from the list of available data.

Table 90-2 Message-Driven EJB Raw Monitoring Data

Run-Time Count | Description
--- | ---
Access Total Count | Displays the total number of times an attempt was made to get an instance from the free pool. This information is useful for giving context to the other free pool counts.
Beans In Use Current Count | Displays the number of bean instances currently in use from the free pool. This information is useful for tracking demand for your EJB. For example, this can be important when investigating an abnormal pool miss ratio.
Destroyed Total Count | Displays the number of bean instances that have been destroyed.
EJB Name | Displays the name of EJB.
Miss Total Count | Displays the total number of times a failed attempt was made to get an instance from the free pool. An Attempt to get a bean from the pool will fail if there are no available instances in the pool. This information is useful for calculating the pool miss ratio.
Pool Timeout Total Count | Displays the total number of Threads that have timed out waiting for an available bean instance from the free pool. This information is useful for calculating the pool timeout ratio.
Pool Waiter Total Count | Displays the total number of threads that have waited for an available bean instance from the free pool.
Pooled Beans Current Count | Displays the current number of available bean instances in the free pool. This information is useful for tracking demand for your EJB. For example, this can be important when investigating an abnormal pool miss ratio.
Server | Displays the server instance upon which the EJB runs.
Transactions Committed Total Count | Displays the total number of transactions that have been committed.
Transactions Rolled Back Total Count | Displays the total number of transactions that have been rolled back.
Transactions Timed out Total Count | Displays the total number of transactions that have timed out.
Waiter Current Count | Displays the number of threads currently waiting for an available bean instance from the free pool. This information may be useful, for example, for investigating the cause of poor application performance at a particular time.

## Tasks

Monitoring EJBs

## Related Topics

Tuning WebLogic Server EJBs in WebLogic Server Performance and Tuning.