This chapter lists some of the frequently asked questions encountered while using Oracle AD4J.
Some of the frequently asked questions include:
What is the meaning of "Cost"?In my console why do I see "No Data Found" in the Java tab?How do I navigate the NOC tab to get to a specific date or time period?Why are the User/Request/IP Addr fields empty in the thread view?How much repository space do I require for monitoring and for heap dumps?How do I install the AD4J Database Agent on Windows?Can I still use AD4J without a database agent?How can I check if my JVM is supported by AD4J?
Where does the Agent Store Its Log Files?
How do I Prevent the Agent from Terminating Program before Thread Execution is Completed?
Cost represents the number of times the agent has seen a given method across all sampled threads. When the polling interval is set to 1 second, this represents approximately the total number of seconds spent in this method across all active threads seen during the total time.
You will see No Data Found in the Java tab on the console if monitoring has not been enabled for the pool currently being viewed. To enable monitoring, do the following:
Click the Setup tab. Then click Console Setup and Enable Monitoring.
Click the Setup tab. Then click Monitoring and Start Monitoring.
Click the Setup tab. Then click JVM Pools and click on the Edit icon. Check the Poll Enabled checkbox.
You may also see this error if your browser cache is corrupted. You must ensure that the browser cache is emptied before retrying this operation.
The three arrow icons on the top left of the NOC view can be used to navigate to different time periods of monitoring. The arrow pointing up is used to zoom out and increase the amount of time being viewed while the left and right arrows allow you to navigate back and forth across different time periods.
Some application servers protect this data and hide it so that is not available to the AD4J Agent. This will cause the fields to appear blank. Additionally, these fields can also appear blank on an application server that is not fully supported by AD4J.
In a standard monitoring setup, at least 25 - 100 MB is required initially with a default 24 hour purge interval. You must check the tablespace growth periodically and if required, you may need to change the space requirements. This will ensure that database growth due to standard monitoring will occur smoothly without sudden spikes.
However, there are 2 things that can drastically affect your tablespace:
Heap Dumps: Analyzing heaps requires a large amount of tablespace. As a standard practice, we recommend that you must have 5 times the size of heap dump file being loaded in your tablespace. Since you know the size of your dump file, make sure that there is adequate space to accommodate the dump file before it is loaded into the database.
Thread Traces: While these are smaller than heaps. they are loaded into the database automatically when a user initiates a trace at the console. The size of these threads can vary dramatically depending on the number of active threads during the trace, the duration of the trace, and the sample interval of the trace. This should usually be under 100MB but if several thread traces have been initiated, it could fill up the database quickly. Before initiating the traces, you must ensure that there is adequate space in the database.
In this release, the AD4J Database Agent cannot be installed on Windows.
Most AD4J functions for monitoring JVMs and databases will work properly without a database agent. But if you encounter a thread that is in the DB Wait state, it will not be a hyperlink. Therefore, you cannot follow the thread into the database and see its database session information including the SQL that it executes. Since the only function of the database agent is to provide cross-tier correlation, the information in the database tab will not be impacted.
The supported JVMs are listed in the README.TXT file available at http://www.oracle.com/technology/software/products/oem/htdocs/jade.html.
All agent logging is done to the STDERR stream which the Application Server redirects to a file. Refer to the Application Server documentation for details on the location of the file in which the STDERR messages are logged.
While monitoring a standalone program with the AD4J agent, the program may get terminated before all the threads have been executed. To prevent this from happening, you need to add jamisdaemon parameter and set the value as jamisdaemon=true. This parameter wil prevent the agent from exiting before all the threads have been completely executed.