Oracle in World: November 2009

Monday, November 30, 2009

Helpctr.exe application error

About Helpctr.exe Process
helpctr.exe (helpctr stands for Microsoft Help and Support Center) is a Windows NT/2000/XP generic process which is loaded in the background when you run Windows Help. When help is requested in Windows 2000 or later version of Windows this process will be initiated. This is a non-essential process which means disabling or enabling it is upon to user preference.

Note that The process helpctr.exe is not a virus or a worm or a Trojan horse or spyware, or adware.

Problem Symptoms:
- I am using Windows XP with service pack 2. when I start my computer the hard drive keep running and it take a lot of time to start windows.

- When I open the task manager by right clicking on the task bar or open the task manager using ctrl+alt+del it shows the helpctr.exe appear in many, many times. In fact all my task manager entry if filled with helpctr.exe process.

- The boxes Helpctr.exe keep coming on the screen. And the following box appeared
helpctr.exe application error-
the application failed to initialize properly(0x000012d) or ((oxc000017, or 0xc000012d142)) Click on OK to terminate the application.
Click on CANCEL to debug the program.

- After another box reads: Microsoft Visual C++ runtime library
runtime error!
Program :C:\Windows\PC HEALTH\ HELPCTR\Binaries\helpctr.exe
This application has requested the Runtime to terminate it in an unusual way. Please contact the applications support team for more information.

- If I want to remove those so many pop up message after clicking either close or ok or cross button one there is another box under it and in fact so many boxes there. If I move that box, there is another box under it. When I click all boxes ok button all pop ups are gone and the screen seems to be normal as well as all of the helpctr.exe entries in Task Manager are gone.

- After I clicked all the pop ups HelpCtr.exe the computer continues to work as usual but suddenly it started same problem frequently pop up window appears one after another. In fact it depends on the application. For example if I open google chrome browser I see lots of google help page appeared there. If I open firefox browser lots of tab containing firefox help page appeared. If I dont open any application frequently windows help and messaging centre window appears. If I push the X in the upper right corner of the help menu the help window closes but then reopens again by itself. if it doesn't reopen by itself it reopens when I click anywhere on the application.

Problem Investigation:
I used windows Search button and searched for helpctr.* and found helpctr.exe exists in about 5 locations. I changed the name to another name of each folder and rebooted. But the problem remained same.

I reinstall windows computer but still no help.

Installed anti virus but no help. Problem remained. I removed helpctr.exe but still same problem

I even deleted my help folder in windows. But still did not solve my problem. It rather looking for the help boxes to pop up (which dont exist anymore). So it will give me an error box about my helpctr.exe application not functioning, but the box will never close. It just keeps popping up over and over again.

I have even tried following steps based on some posts suggestion after searching google but still that did not solve the problem. What I did is to delete the help cache files in your user profile directory.

1. Start Windows Explorer

2. The files are in a hidden directory, so you will need to enable to view the hidden files. In the Windows Explorer do following to enable viewing on hidden files.
Tools -> Folder Options -> View ->
From Advanced settings Hidden files and folders:
Select Show hidden files and folders
Click ok.

3. Then you will have to go into your user profile's help cache location. This is normally at the following location:
<Windows Installation Directory>\Documents and Settings\<USERNAME>\Application Data\Microsoft\HTML Help\

Where <Windows Installation Directory> is like C: or D:
and <USERNAME> is your windows login name.

4. Delete all the files you find in the above folder. You may wish to make a backup first. Simply copy the folder to another location.

You will see your problem may disappeared temporary but it is not permanent solution.

Solution of the Problem
After pop up keep opening I pressed many keys at a time and I see problem stops. And I tried to understand for which keystroke the problem stops. I also see all the time help related page and error appeared. So I guess the F1 key might be the culrpit. From my keyboard I removed F1 key and it worked really. So you have two solutions of the above problem. As this problem is hardware problem and specifically your keyboard's F1 is the culprit so either replace your keyboard with a new one and repair your keyboard so that F1 key does not keep pressed. In fact the problem arises since F1 key pressed continuously.

Related Documents
http://arjudba.blogspot.com/2009/07/disable-skype-from-using-opening-or.html
http://arjudba.blogspot.com/2009/07/how-to-check-or-identify-which-process.html
How to know process ID or PID on windows
How to Use Special Characters in Windows
Natural Windows Keyboard Shortcut
Dialog Box and Accessibility Keyboard Shortcut
Windows Explorer Keyboard Shortcut

Thursday, November 26, 2009

EID Ul Azha Mubarak to my readers

As a Muslim I am about to celebrate Eid Ul Azha (also called as Eid Ul Adha). Eid Ul Azha is called "Festival of Sacrifice" or "Greater Eid". I here wish a happy and peaceful EID to everyone in the world. May this EID day brings joyful life to all of you. To my reader I am here to attach some of the EID cards from me.

Wednesday, November 25, 2009

EMCA fails with ORA-06502 PL/SQL: numeric or value error: character string buffer too small

Problem Description
While configuring dbconsole using following command,
emca -config dbcontrol db -repos create

It shows following messages

Do you wish to continue? [yes(Y)/no(N)]: yes

Do you wish to continue? [yes(Y)/no(N)]: yes
Nov 25, 2009 9:21:10 AM oracle.sysman.emcp.EMConfig perform
INFO: This operation is being logged at /opt/oracle/app/oracle/oracle/product/10.2.0/db_1/cfgtoollogs/emca/EAIAPP/emca_2009-11-25_09-18-57-AM.log.
Nov 25, 2009 9:21:13 AM oracle.sysman.emcp.EMReposConfig createRepository
INFO: Creating the EM repository (this may take a while) ...
Nov 25, 2009 9:26:30 AM oracle.sysman.emcp.EMReposConfig invoke
SEVERE: Error creating the repository
Nov 25, 2009 9:26:30 AM oracle.sysman.emcp.EMReposConfig invoke
INFO: Refer to the log file at /opt/oracle/app/oracle/oracle/product/10.2.0/db_1/cfgtoollogs/emca/EAIAPP/emca_repos_create_.log for more details.
Nov 25, 2009 9:26:30 AM oracle.sysman.emcp.EMConfig perform
SEVERE: Error creating the repository
Refer to the log file at /opt/oracle/app/oracle/oracle/product/10.2.0/db_1/cfgtoollogs/emca/EAIAPP/emca_2009-11-25_09-18-57-AM.log for more details.
Could not complete the configuration. Refer to the log file at /opt/oracle/app/oracle/oracle/product/10.2.0/db_1/cfgtoollogs/emca/EAIAPP/emca_2009-11-25_09-18-57-AM.log for more details.

And fails with above error message.

From the logfile it shows followings, /opt/oracle/app/oracle/oracle/product/10.2.0/db_1/cfgtoollogs/emca/EAIAPP/emca_2009-11-25_09-18-57-AM.log it shows followings.

CONFIG: Setting param: RMI_PORT_EAIAPP value: 5520
Nov 25, 2009 9:21:12 AM oracle.sysman.emcp.EMDBPreConfig getFreePorts
CONFIG: Ports assigned for SID: EAIAPP : {DBCONTROL_HTTP_PORT=1158, RMI_PORT=5520, JMS_PORT=5540, AGENT_PORT=3938}
Nov 25, 2009 9:21:12 AM oracle.sysman.emcp.util.GeneralUtil initSQLEngine
CONFIG: SQLEngine connecting with SID: EAIAPP, oracleHome: /opt/oracle/app/oracle/oracle/product/10.2.0/db_1, and user: SYS
Nov 25, 2009 9:21:13 AM oracle.sysman.emcp.util.GeneralUtil initSQLEngine
CONFIG: SQLEngine created successfully and connected
Nov 25, 2009 9:21:13 AM oracle.sysman.emcp.EMReposConfig createRepository
CONFIG: Spooling to /opt/oracle/app/oracle/oracle/product/10.2.0/db_1/cfgtoollogs/emca/EAIAPP/emca_repos_create_2009-11-25_09-21-13-AM.log
Nov 25, 2009 9:21:13 AM oracle.sysman.emcp.EMReposConfig createRepository
INFO: Creating the EM repository (this may take a while) ...
Nov 25, 2009 9:26:30 AM oracle.sysman.emcp.EMReposConfig createRepository
CONFIG: ORA-06502: PL/SQL: numeric or value error: character string buffer too small
ORA-06512: at line 259
CONFIG: ORA-06502: PL/SQL: numeric or value error: character string buffer too small
ORA-06512: at line 259

oracle.sysman.assistants.util.sqlEngine.SQLFatalErrorException: ORA-06502: PL/SQL: numeric or value error: character string buffer too small
ORA-06512: at line 259

   at oracle.sysman.assistants.util.sqlEngine.SQLEngine.executeImpl(SQLEngine.java:1474)
   at oracle.sysman.assistants.util.sqlEngine.SQLEngine.executeScript(SQLEngine.java:848)
   at oracle.sysman.assistants.util.sqlEngine.SQLPlusEngine.executeScript(SQLPlusEngine.java:267)
   at oracle.sysman.assistants.util.sqlEngine.SQLPlusEngine.executeScript(SQLPlusEngine.java:308)
   at oracle.sysman.emcp.EMReposConfig.createRepository(EMReposConfig.java:422)
   at oracle.sysman.emcp.EMReposConfig.invoke(EMReposConfig.java:192)
   at oracle.sysman.emcp.EMReposConfig.invoke(EMReposConfig.java:134)
   at oracle.sysman.emcp.EMConfig.perform(EMConfig.java:171)
   at oracle.sysman.emcp.EMConfigAssistant.invokeEMCA(EMConfigAssistant.java:486)
   at oracle.sysman.emcp.EMConfigAssistant.performConfiguration(EMConfigAssistant.java:1142)
   at oracle.sysman.emcp.EMConfigAssistant.statusMain(EMConfigAssistant.java:470)
   at oracle.sysman.emcp.EMConfigAssistant.main(EMConfigAssistant.java:419)
Nov 25, 2009 9:26:30 AM oracle.sysman.emcp.EMReposConfig invoke
SEVERE: Error creating the repository
Nov 25, 2009 9:26:30 AM oracle.sysman.emcp.EMReposConfig invoke
INFO: Refer to the log file at /opt/oracle/app/oracle/oracle/product/10.2.0/db_1/cfgtoollogs/emca/EAIAPP/emca_repos_create_.log for more details.
Nov 25, 2009 9:26:30 AM oracle.sysman.emcp.EMConfig perform
SEVERE: Error creating the repository
Refer to the log file at /opt/oracle/app/oracle/oracle/product/10.2.0/db_1/cfgtoollogs/emca/EAIAPP/emca_2009-11-25_09-18-57-AM.log for more details.
Nov 25, 2009 9:26:30 AM oracle.sysman.emcp.EMConfig perform
CONFIG: Stack Trace:
oracle.sysman.emcp.exception.EMConfigException: Error creating the repository
   at oracle.sysman.emcp.EMReposConfig.invoke(EMReposConfig.java:204)
   at oracle.sysman.emcp.EMReposConfig.invoke(EMReposConfig.java:134)
   at oracle.sysman.emcp.EMConfig.perform(EMConfig.java:171)
   at oracle.sysman.emcp.EMConfigAssistant.invokeEMCA(EMConfigAssistant.java:486)
   at oracle.sysman.emcp.EMConfigAssistant.performConfiguration(EMConfigAssistant.java:1142)
   at oracle.sysman.emcp.EMConfigAssistant.statusMain(EMConfigAssistant.java:470)
   at oracle.sysman.emcp.EMConfigAssistant.main(EMConfigAssistant.java:419)

Cause of the Problem
There is a bug during the create of the EM Repository. Somehow terrible oracle bug :).
When hostname exceeds 32 characters emca will fail with
ORA-06502 PL/SQL: numeric or value error: character string buffer too small

Now let's verify it. From OS, you can simply do this by issuing hostname.
EAIAPP:/home/oracle>hostname
db1-eai.test1.hrn.eai.clearditlab.com

Unfortunately our database name is more than 32 characters and hence bug fired. You can also check the database hostname and length using following query,

sqlplus / as sysdba
SQL> set line 200
SQL> select host_name,length(host_name),instance_name from v$instance where rownum=1;

By both ways we see that our hostname is more than 32 characters and our bug fired.

Solution of the Problem
In order to avoid the bug you either need to change the hostname of the operating system. In order to change hostname on linux environment you have to look at http://arjudba.blogspot.com/2008/08/how-to-change-hostname-in-linux.html

If you don't want to change hostname you can bypass this bug by apply the following steps:

1) Drop the repository with emca
emca -deconfig dbcontrol db -repos drop

2) cd to $ORACLE_HOME/sysman/admin/emdrep/sql/core/latest/self_monitor/

cd $ORACLE_HOME/sysman/admin/emdrep/sql/core/latest/self_monitor/

3) Make a copy of self_monitor_post_creation.sql
cp self_monitor_post_creation.sql self_monitor_post_creation.sql.bak

4) Edit the script and change the l_host_name from varchar2(32) to higher varchar2 for example varchar2(128).
l_host_name varchar2(128)
Note: The l_host_name variable is declared 2 times in the script.

5) Create repository with emca
emca -config dbcontrol db -repos create

And now you are done.

Related Documents
http://arjudba.blogspot.com/2008/04/troubleshooting-dbconsole-error-oc4j.html
http://arjudba.blogspot.com/2008/04/how-to-drop-create-and-recreate-db.html
http://arjudba.blogspot.com/2008/04/stack-of-problems-while-creating.html

Tuesday, November 24, 2009

Best SEO tips to increase your website traffic

Top SEO tips to increase your website traffic.

1)Research Keywords:
Before writing any articles first check the keywords for which it is searched
heavily. Writing articles that is not search much by peoples will not probably drive any traffic to
your site. Google has a free keyword tool by which you can have an idea about the lists of keywords
that is searhed by people. You can have access the tool by visiting link https://adwords.google.com/select/KeywordToolExternal
From the tool you will also get an idea about Local Search Volume of last month, Global search volume,
Advertiser competition, Average CPC rate, Search volume trends etc. From the google keyword tool,
a) After putting your desired keywords Download the sheet in an excel sheet.
b) Find out your kind of keywords (that match your website content and products).
c) Sort them by daily searches.

2)Write original and optimized content:
User as well as SEO like original contents. Also make sure not to violate google webmaster guidelines.
Before writing any contents make sure you read their webmaster guidelines. An intelligent SEO writers
keep the right balance of keywords throughout the contents. Don't use SEO keywords too much. In general
it is good idea to keep 5% to 10% usage of keywords to write SEO articles.

3)Optimize your webpage:
Put the keywords in Title, Description and add more keywords in the keywords area.
Properly use H1 to H6 tags. Note that Alt Tags must be placed on the images wherever possible.
I have listed optimization of webpage topics in the post http://arjudba.blogspot.com/2009/11/affordable-search-engine-optimization.html

4)Do offpage promotion for your website:
After you write good content, doing onpage /webpage optimization now go for offpage optimization. There
are many companies who do affordable Search engine optimization offpage process. You can check a list of
off page process list from http://arjudba.blogspot.com/2009/10/seo-link-building-directory-article.html

5)Use tools to monitor your site:
Make sure you have installed google analytics, google webmaster tools
to monitor your site. Google webmaster tools allow webmasters to check indexing status and optimize
visibility of their websites.

It also let webmasters know about
- Check and set the crawl rate
- List internal and external pages that link to the site
- See what keyword searches on Google led to the site being listed in the SERPs,
and the click through rates of such listings
- View statistics about how Google indexes the site
- Submit and check a sitemap
- Generate and check a robots.txt file
- Set a preferred domain, that is with www or without www.
- Any crawl error, keyword significance for your site.
- List of sitelinks generated for your site and let it allow to block any sitelink.
- Parameter suggetions like start index.
- Top search queries that resulted your site appear in google search in terms of impressions
as well as clicked to your site.
- List the google subscribers statistics of your site.
- Provide any HTML suggestions like to detect any potential issues with content on your pages,
including duplicate, missing, or problematic title tags or meta descriptions.

In the post http://arjudba.blogspot.com/2009/07/how-to-setup-google-webmaster-tool-for.html it is described how to setup google webmaster tools.

Related Documents

http://arjudba.blogspot.com/2009/10/seo-link-building-directory-article.html
http://arjudba.blogspot.com/2009/11/list-of-social-bookmarking-site-in.html
http://arjudba.blogspot.com/2009/11/list-of-social-bookmarking-site-by.html
http://arjudba.blogspot.com/2009/11/social-bookmarking-site-by-language.html
http://arjudba.blogspot.com/2009/11/how-to-check-nofollow-or-dofollow-links.html
http://arjudba.blogspot.com/2009/11/affordable-search-engine-optimization.html
http://arjudba.blogspot.com/2009/07/how-to-setup-google-webmaster-tool-for.html

Monday, November 16, 2009

Affordable Search Engine Optimization Services Packages

If you ever want SEO services for your website then probably you have appeared in the correct place. :) Before introducing our list of SEO packages, let me suggest you a good list of advice which will help your site to appear good position in search engine.

1. Always choose a short domain name. Customers love to type short domain name in their browser address bar. If you don't find any short domain name then choose a domain name that best describes your product.

2. Always use <TITLE> tag in each of your browser page and make it unique as well as accurate because title tag tells both users and search engines about the topic of a particular page is. Also make sure your title is not too long but informative.

3. Make use of the "DESCRIPTION" meta tag. A web page's DESCRIPTION meta tag gives Google and other search engines a summary of what the page is about. TITLE can be short but DESCRIPTION may be a one or two two sentences or a short paragraph. Note that use unique description in each of your web page.

4. Make search engine friendly as well as user friendly url. Use word in place of number to form a url. Use directory structure to build a url. For example,
http://www.arju-on-it.com/forum/server-administration/how-to-change-global-name-in-database/ is more friendly url for user as well as search engine than if we would use simply http://www.arju-on-it.com/8780098.html .
Also note that the directory hierarchy; it goes to forum/server-administration.

5. Make sure your site is easier to navigate. In this way user can easily find the page as well as search engine can better understand and rank of your pages.

6. Creating an XML Sitemap file for your site which ensure that search engines discover the pages on your site.

7. If any url not found in your site redirect it to a good and useful page instead of showing 404 "Not Found" page.

8. Use better heading text, best use alt tag for image, use proper anchor text.

9. Make use of google webmaster tool, google analytics tool. Setup about google webmaster tool is discussed in http://arjudba.blogspot.com/2009/07/how-to-setup-google-webmaster-tool-for.html.

10. With assistant of any good SEO specialist promote your page.

Our company will take care all above 10 steps and so I am going to present here a list of affordable search engine optimization services packages.

A)Bronge Packages - Price $50/per month (We recommend for 6 months)
1. Initial Analysis, Target and research 5 Keywords or phrases.
2. Competitor Analysis, their metatags analysis.
3. Meta tag Composition.
4. Suggest Content Density, Alt and Anchor Text.
5. Manual Submission to top search engines.
6. Manual submissions to 10 individual web directories.
7. Generate XML Sitemap.

B)Silver Packages - Price $220/per month (We recommend for 6 months)
1. Initial Analysis, Target and research 5 Keywords or phrases.
2. Competitor Analysis, their metatags analysis.
3. Meta tag Composition.
4. Suggest Content Density, Alt and Anchor Text.
5. Homepage url and Inner page url analysis.
6. Manual Submission to top search engines.
7. Manual submissions to 1000 individual web directories.
8. Manual submissions to 100 social bookmarking websites.
9. Manual submissions to 60 article directories.
10.Website Review
11.SEO Site Map generation.
12.SEO Navigation Optimization
13.Set up google analytics, google webmaster tools.
14.Generate XML Sitemap and add it to google webmaster tools.
15.Search Engine Ranking Reports

C)Gold Packages - Price $400/per month (We recommend for 6 months)
1. Initial Analysis, Target and research 10 Keywords or phrases.
2. Competitor Analysis, their metatags analysis.
3. Meta tag Composition.
4. Suggest Content Density, Alt and Anchor Text.
5. Homepage url and Inner page url analysis.
6. Manual Submission to top search engines.
7. Manual submissions to 2000 individual web directories.
8. Manual submissions to 200 social bookmarking websites.
9. Manual submissions to 120 article directories.
10.Website Review.
11.SEO Site Map generation.
12.SEO Navigation Optimization.
13.Set up google analytics, google webmaster tools.
14.Generate XML Sitemap and add it to google webmaster tools.
15.Search Engine Ranking Reports.

D)Gold Packages - Price $600/per month (We recommend for 6 months)
1. Initial Analysis, Target and research 15 Keywords or phrases.
2. Competitor Analysis, their metatags analysis.
3. Meta tag Composition.
4. Suggest Content Density, Alt and Anchor Text.
5. Homepage url and Inner page url analysis.
6. Manual Submission to top search engines.
7. Manual submissions to 3000 individual web directories.
8. Manual submissions to 300 social bookmarking websites.
9. Manual submissions to 200 article directories.
10.Website Review.
11.SEO Site Map generation.
12.SEO Navigation Optimization.
13.Set up google analytics, google webmaster tools.
14.Generate XML Sitemap and add it to google webmaster tools.
15.Search Engine Ranking Reports.

E)Diamond Packages - Price $800/per month (We recommend for 6 months)
1. Initial Analysis, Target and research 20 Keywords or phrases.
2. Competitor Analysis, their metatags analysis.
3. Meta tag Composition.
4. Suggest Content Density, Alt and Anchor Text.
5. Homepage url and Inner page url analysis.
6. Manual Submission to top search engines.
7. Manual submissions to 4000 individual web directories.
8. Manual submissions to 400 social bookmarking websites.
9. Manual submissions to 320 article directories.
10.Website Review.
11.SEO Site Map generation.
12.SEO Navigation Optimization.
13.Set up google analytics, google webmaster tools.
14.Generate XML Sitemap and add it to google webmaster tools.
15.Search Engine Ranking Reports.

F)Platinum Packages - Price $1000/per month (We recommend for 6 months)
1. Initial Analysis, Target and research 25 Keywords or phrases.
2. Competitor Analysis, their metatags analysis.
3. Meta tag Composition.
4. Suggest Content Density, Alt and Anchor Text.
5. Homepage url and Inner page url analysis.
6. Manual Submission to top search engines.
7. Manual submissions to 4000 individual web directories.
8. Manual submissions to 400 social bookmarking websites.
9. Manual submissions to 320 article directories.
10.100 Blog Commenting.
11.50 Forum Posting.
12.Description, Title suggestion of the webpages.
13.Website Review.
14.SEO Site Map generation.
15.SEO Navigation Optimization.
16.Set up google analytics, google webmaster tools.
14.Generate XML Sitemap and add it to google webmaster tools.
15.Search Engine Ranking Reports.

However if you care about any individual package and about their pricing please have a look at http://arjudba.blogspot.com/2009/10/seo-link-building-directory-article.html

Finally, you are welcome to work with us. If you want to work with us just mail me a_arju@yahoo.co.uk or you can reach me through my cell at +8801710282272.

Related Documents
http://arjudba.blogspot.com/2009/06/how-to-get-targeted-backlinks-to-your.html

http://arjudba.blogspot.com/2009/06/how-to-get-targeted-backlinks-to-your.html

http://arjudba.blogspot.com/2009/10/seo-link-building-directory-article.html

http://arjudba.blogspot.com/2009/11/list-of-social-bookmarking-site-in.html

http://arjudba.blogspot.com/2009/11/list-of-social-bookmarking-site-by.html

http://arjudba.blogspot.com/2009/11/social-bookmarking-site-by-language.html

http://arjudba.blogspot.com/2009/11/how-to-check-nofollow-or-dofollow-links.html

Sunday, November 15, 2009

List of Oracle Networking Components

Oracle provide following networking components which help to build up network services between application client and oracle database server.

1) Oracle Net
2) Oracle Net Listener
3) Oracle Connection Manager
4) Networking Tools
5) Oracle Advanced Security

1) Oracle Net:
Oracle Net is software layer that resides on the client and the Oracle database server.
It is responsible for establishing and maintaining the connection between the client
application and oracle server, as well as exchanging messages between them.
Oracle Net has two software components.
a)Oracle Net Foundation Layer.
b)Oracle Protocol Support.

How Connection is established
- On the client side, client application communicates with Oracle Net Foundation Layer to establish and maintain connections.

- Oracle Foundation Layer then uses Oracle Protocol Support which in turn communicate with Oracle Database Server.

- Oracle Protocol Support uses any Network protocol (for example TCP/IP) in order to transfer request from client to Server.

- On the server side request from Network protocol is transferred to Oracle Protocol Support Layer which then passes request to Oracle Net Foundation Layer.

- Oracle Net foundation layer then communicates with the Oracle database server to
process the client request.

Here is the list of Network protocol that is supported by Oracle Protocol Support.
- TCP/IP
- TCP/IP with SSL
- Named Pipes
- SDP

2) Oracle Net Listener:
Oracle Net Listener also called simply listener only resides in oracle server. It acts as brokers of a client request, handing off the request to the server. The listener is configured with a protocol address. Clients configured with the same
protocol address can send connection requests to the listener. Once a connection is
established, the client and Oracle database server communicate directly with one another.

3) Oracle Connection Manager:
Oracle Connection Manager is a software component that resides neither in client computer nor in an Oracle database server. It proxies and screens requests for the database server. Also, it multiplexes database sessions.

It funnels multiple sessions through a single transport protocol connection to a particular destination. This reduces the demand on resources needed to maintain multiple sessions between two processes by enabling the Oracle database server to use fewer connection end points for incoming requests.

4) Networking Tools:
Oracle Net Configuration Assistant(netca) is a tool that enables you to configure
listeners and naming methods. You can access Net Configuration Assistant by simply typing netca in the command prompt.

5) Oracle Advanced Security:
Oracle Advanced Security is a separately licensable product that provides a comprehensive suite of security features for the Oracle environment.
Related Documents
http://arjudba.blogspot.com/2008/08/configure-network-for-oracle-rac.html

ORA-12560: TNS:protocol adapter error on windows machine while starting oracle
ORA-12514: TNS:listener does not currently know of service requested in connect descriptor
Startup fails with oracle error ORA-00119, ORA-00132

http://arjudba.blogspot.com/2009/11/network-connection-in-oracle-using.html