Databases Reference
In-Depth Information
The Flight Recorder is enabled and configured to store the last 24 hours of events, or until
the file size reaches 100 MB. The objective is to record the previous events like an airplane's
black box.
There are many settings you can change for the Flight Recorder. The parameters can be
altered to save the events during the entire life cycle of the JVM. Change the
maxage
and
size
parameters to
0
as shown in the following line of code:
-XX:FlightRecorderOptions=defaultrecording=true,disk=true,
repository=./jfr/PROD_Server0X,maxage=0,size=0
For every new recording, a new directory with the pattern
$DOMAIN_HOME/jrf/<SERVER_
NAME>/YYYY_MM_DD_HH_MM_SS_PID
is created.
YYYY
stands for the year,
MM
stands for
the month,
DD
for the day,
HH
for the hour,
SS
for the second, and
PID
is the process ID of the
WebLogic Managed Server.
The file has a similar pattern
YYYY_MM_DD_HH_MM_SS_PID.jfr
and it must be opened in
the JRockit Mission Control to be analyzed. The content of the Mission Control Management
Console is mostly the same, but it can include more information depending on the
configuration template used to save the
.jfr
ile.
See also
F
Analyzing a heap dump
Analyzing a heap dump
A heap dump is another important feature of the Java Virtual Machine. It contains a memory
dump of all the current live Java objects of the heap.
The heap dump is useful in problematic situations, such as in a memory leak condition in a
WebLogic Server where the heap usage grows until the JVM crashes by Out of Memory (OOM),
or when the heap utilization is so high that the Managed Server hangs and stops responding.
Both scenarios can use a heap dump to discover the offender objects in the heap.
This recipe will display how to take a heap dump from a Managed Server in the HPROF format.
HPROF is a binary file that stores the heap and CPU profiles of the JVM. For demonstration
purposes, the heap dump was taken from a JVM configured to a small heap with a maximum
size of 256 MB (
-Xmx256mb
).
Getting ready
The heap dump can be taken from the shell using the
jrcmd
command-line tool or from the
Mission Control.
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