Learning Statistics

I've recently taken an interest in statistics and I'm making efforts to learn more about the subject. One useful Internet resource is the Australian Bureau of Statistics web site.

In particular, The 'Understanding statistics' page aims to support your statistical literacy development and assist you understand, evaluate and communicate statistical data and information. Data sets are also available from the ABS web site which can be used in a statistical context to learn and consolidate ones knowledge of the subject.

Keywords: abs statistics australian bureau

"Superfish" adware

"Superfish" adware that bypasses SSL security. Superfish has been reported to be pre-installed on several 3rd Party laptops. The adware is known to inject third-party ads on Google searches and websites without the user's permission. The article also mentions how to remove the adware.

Click here to read the article.


Keywords: adware superfish ssl security

Business letter writing phrases

The following URL is a useful reminder of business letter phrases particularly in respect of 'Yours faithfully or Yours sincerely; Dear Sir or Dear Mr'.

http://speakspeak.com/resources/general-english-vocabulary/business-letter-writing-phrases

Keywords: salutation

PuTTY colors

Some favourite PuTTY colors.

Window size: 110/35

Foreground color: 232/218/153

Cursor color: 255/0/255

See also

PuTTY Download Page

Keywords: unix linux putty colors

Database normalization

Database normalization is the process of organizing the attributes and tables of a relational database to minimize data redundancy.


Keywords: database normalization

SQL Server PowerShell

SQL Server 2014 supports Windows PowerShell, which is a powerful scripting shell that lets administrators and developers automate server administration and application deployment.

This site covers articles such as SQLPS, SMO Assemblies and using PowerShell with SQL Server.

Click here to go to the site.



Keywords: powershell sqlserver sqlps smo

TCP states

A connection progresses through a series of states during its lifetime. The states are: LISTEN, SYN-SENT, SYNRECEIVED, ESTABLISHED, FIN-WAIT-1, FIN-WAIT-2, CLOSE-WAIT, CLOSING, LAST-ACK, TIME-WAIT, and the fictional state CLOSED. CLOSED is fictional because it represents the state when there is no TCB, and therefore, no connection.

• CLOSED: There is no connection.
• LISTEN: The local end-point is waiting for a connection request from a remote end-point i.e. a passive open was performed.
• SYN-SENT: The first step of the three-way connection handshake was performed. A connection request has been sent to a remote end-point i.e. an active open was performed.
• SYN-RECEIVED: The second step of the three-way connection handshake was performed. An acknowledgement for the received connection request as well as a connection request has been sent to the remote end-point.
• ESTABLISHED: The third step of the three-way connection handshake was performed. The connection is open.
• FIN-WAIT-1: The first step of an active close (four-way handshake) was performed. The local end-point has sent a connection termination request to the remote end-point.
• CLOSE-WAIT: The local end-point has received a connection termination request and acknowledged it e.g. a passive close has been performed and the local end-point needs to perform an active close to leave this state.
• FIN-WAIT-2: The remote end-point has sent an acknowledgement for the previously sent connection termination request. The local end-point waits for an active connection termination request from the remote end-point.
• LAST-ACK: The local end-point has performed a passive close and has initiated an active close by sending a connection termination request to the remote end-point.
• CLOSING: The local end-point is waiting for an acknowledgement for a connection termination request before going to the TIME-WAIT state.
• TIME-WAIT: The local end-point waits for twice the maximum segment lifetime (MSL) to pass before going to CLOSED to be sure that the remote end-point received the acknowledgement.

The following URL's help explain these TCP states.

TCP/IP State Transition Diagram (RFC793)
http://www.cs.northwestern.edu/~agupta/cs340/project2/TCPIP_State_Transition_Diagram.pdf

TCP states
http://benohead.com/tcp-about-fin_wait_2-time_wait-and-close_wait/

See also

The TCP/IP model
http://www.cs.northwestern.edu/~agupta/cs340/project2/TCPIP_State_Transition_Diagram.pdf

Oracle SQL Plan Stability

Tanel Poder has written an article on his blog on the subject of Oracle SQL Plan Stability. The article contains a number of useful links to other pages on the subject.

Click here for the article.


See also

Tanel Poder's blog.

Oracle performance and O/S Statistics

Operating system statistics provide information on the usage and performance of the main hardware components of the system, as well as the performance of the operating system itself.

Operating System Data Gathering Tools:

• CPU - sar, vmstat, mpstat, iostat
• Memory - sar, vmstat
• Disk - sar, iostat
• Network - netstat

Reference
Oracle Database Performance Tuning Guide

Product Documentation

Microsoft SQL Server online documentation can be found here. This facility covers the current and previous versions.


Oracle online documentation can be found here. This repository of information covers the Oracle Portfolio rather than just database systems. Areas covered for example, are Cloud, Big Data, Hardware and Java.




Keywords: sqlserver documentation oracle

PowerShell scripts

The following two sites are worth looking at for PowerShell scripts and inspiration.



1.
Microsoft Script Center
Script resources for IT professionals

Summary

At the Microsoft Script Center, we are dedicated to the system administrator scripters of the world whom we teach how to use Windows PowerShell to reduce time spent performing mundane tasks.

https://gallery.technet.microsoft.com/scriptcenter

2.

PowerShell Code Repository

Summary

PoshCode is a repository of PowerShell scripts that are free for public use. As you find things useful, we only ask that you give back to our community.

http://poshcode.org/

Keywords: powershell ps1 scripts

CRA Information

To get a copy of the information that the CRA's have about you, you can contact them at:

Experian Ltd

http://www.experian.co.uk/

Equifax Ltd

http://www.equifax.co.uk/

Callcredit Plc

http://www.callcredit.co.uk/