What is problem determination

greasyservantInternet and Web Development

Jul 30, 2012 (4 years and 10 months ago)

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What is problem determination?

Problem determination includes debugging applications, but also diagnosing the system
at large by investigating product configurations and verifying the means by which all of
the system’s components interact.



The problem d
etermination process

Unable to start a component


Hanging component


Crashing component


Misbehaving component



The above problems may be due to one or more of the following.


Misconfiguration


Lack of resources


Programming error, such as



Memory leak



Dead lock



Synchronization


Product defect




The problem determination process

Step1:

Identifying the problem
(
and able to recreate it at will
)
.

Step 2:

Repetition
(by reducing the complexity and using different scenarios)

Step 3:

Collect logs
, read

and correlate them.

Step 4:

Isolate the offending component

Step 5:

Fix the problem
(
Product defects are fixed thru e
-
fixes
)
.



Key points for websphere problem determination

Major
Key

points

Understand how the software works under the covers, how messa
ges are passed from one
component to another, and how one component interacts with another component.

Be careful about assumptions. Only report and log what you can verify.

What is different today from yesterday? (Look at those change logs).

Can you repr
oduce the problem? If so, it will be much easier to solve.

Does this problem affect only this user or this workstation? This helps determine where
to look

Describe the symptoms of the problem in detail with precise descriptions. Ambiguity will
cause ser
ious problems later.

If there are multiple problems, try to separate them and deal with them independently.

Find the possible causes for the symptoms.

When testing, limit the number of changes made before a test (do not change many
parameters at once).

Keep a log of symptoms, messages, files, tests, results from tests, and conclusions.

Retrace the steps described to recreate the problem and see the results yourself.

Understand the meaning behind the request that has created or induced the problem, this
will help you isolate the problem.

Use a controlled test environment when possible.

Find out what is NOT part of the problem. This will help you eliminate variables in an
already complex equation.

Follow the problem determination method.

Download the l
atest symptoms database, reproduce the problem, and run Log Analyzer
over your activity.log file. This will allow you to check for known errors much more
efficiently and effectively because Log Analyzer has a symptoms database which
matches known problems
to your current websphere problem as noted by the activity.log.
Resolutions based on the problems are available with the symptom database, which might
entail the next step after running Log Analyzer


checking the e
-
fix website.


Check the e
-
fix website








Key points to remember about WAS5.0

Notes on test and production environments

Things to have when working a problem


Websphere problem determination and isolation


Introduction to WAS 5.0


Admin server


Application server


Http server and websp
here http server plug
-
in


Embedded http server


Application code running in the web container and EJB container

Basic problem determination for configuration and administration


Installation problems


Starting the websphere admin server


Starting the w
ebsphere admin console


Starting wsadmin in interactive mode


Running XML Config


Start the application server



Basic problem determination for HTTP requests

JVM crashes and hangs


Admin server crashes and hangs


App server crashes and hangs



Memory lea
ks


Application heap leaks


Native heap leaks

Websphere session affinity


Servlet workload management


EJB workload management










The HTTP server plug
-
in

Understanding the plug
-
in


The plugin
-
cfg.xml file


Expected behavior of the plug
-
in

Tro
ubleshooting the plug
-
in


The http server will not start


Native.log contains entries about the configuration errors


Changes were made to the plug
-
in configuration, but plug
-
in behavior has not
changed.



Browser clients cannot reach web application


“I
nternal Server Error” message in browser (a.k.a HTTP error 500)


“404 File Not Found” message in browser


The plug
-
in is not communicating with the application server


Requests are not distributed to all clones


Session affinity problems


Plug
-
in logs and

traces


The plug
-
in log file


Tracing the plug
-
in


Reading plug
-
in logs and traces


Web server log files

Plug
-
in problem determination examples


“404 file not found” error scenario


Improper workload management scenario
.





























Diff
erences between V4.0 and V5.0

Memory leaks

Tivoli performance monitoring

How to deploy an application

What factors are considered in clustering?

What parameters are used in tuning?

Adv of vertical and horizontal scaling

Deploy an EJB

How is security ac
hieve

Performance tools

JMS security enable

Tuning parameter with respect Solaris

When or under what conditions your app server freeze.