E-Systems in Computer Sciences

1. COMP 0161: E-Systems
E.R
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2. Introduction to Transaction Processing
 What is a transaction: - a sequence of information exchange and related
work (such as database updating) that is treated as a unit for the purposes
of satisfying a request and for ensuring database integrity
 What is transaction process is a term that refers to the adding, changing,
deleting, or looking up of a record in a data file or database by entering
the data at a terminal or workstation.
 What is transaction processing system: - TPS is a system that captures,
enters, stores, retrieves, and processes the relevant details of business
events, and generates the information/documents necessary for running
the organization and interfacing with external entities, such as customers.
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3. Processing part of the TPS
 Capturing the data as close to the source as possible
 Entering them into the system in a manner as effectively and
efficiently as possible
 Storing them in the database
 Retrieving them from the database for further processing
 Transforming them from the raw form to information useful to the
intended user
 systems part of the TPS has to do with planning and designing the
above elements so that they work in sync to produce the
organizational objectives behind the TPS.
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4. Transaction part of the TPS
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TPSs are characterized by:-
• Large amounts of input/output
• Large number of users
• Huge storage requirements
• Low computational complexity
• Fast input/output as well as processing capabilities
• A high degree of concern for potential security related
problems
• A high degree of concern for reliability and fault
tolerance.

5. Properties of a transaction
 Atomicity means that actions can be grouped together, and either all actions
in that group will occur or none will.
 Consistency means that the transaction must represent a correct
transformation from one state to another. For example, if a TPS credits one
account in a financial transfer, it must debit the other by the same amount.
 Isolation means that actions do not interfere with each other. Multiple,
simultaneous transactions must be made to appear as if they are actually a
series of sequential transactions. If several users want to access the same bank
account at the same time, the requests must be serialized and treated
independently. Even if actions appear to happen simultaneously to the end
users, they must be serialized and isolated internally.
 Durability means that once a change is made, it is not undone by a system
failure. Changes to data must remain permanent once they are made.
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6. Transaction processing systems five-stage cycle
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7. Processing types
 Batch processing is execution of a series of programs on a computer
without manual intervention. The results of each transaction are not
immediately available when the transaction is being entered there is a
time delay.
 Real time systems attempt to guarantee an appropriate response to a
stimulus or request quickly enough to affect the conditions that
caused the stimulus. Each transaction in real-time processing is
unique; it is not part of a group of transactions.
 Time sharing is the sharing of a computer system among multiple
users, usually giving each user the illusion that they have exclusive
control of the system. The users may be working on the same project
or different projects, but there are usually few restrictions on the type
of work each user is doing.
 A Transaction Processing System (TPS) is a type of information system
that collects, stores, modifies and retrieves the data transactions of
an enterprise.
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8. Network infrastructure
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Network infrastructure is the
hardware and software resources of
an entire network that enable
network connectivity, communication,
operations and management of an
enterprise network.
It contains:
•Networking Hardware
•Networking Software
•Networking Services

10. Networking Hardware:
•Routers: - a networking device that forwards data packets
between computer networks. Routers perform the "traffic
directing" functions on the Internet.
•Switches:- a device that connects devices together on a
computer network, by using packet switching to receive, process
and forward data to the destination device
•NIC: - is a computer hardware component that allows a
computer to connect to a network
•Bridge: - a device that connects multiple network segments
•Cables

11. Networking Software:
 Network operating system (NOS): - specialized operating system for a
network device such as a router, switch or firewall. It provides the
mechanism to integrate all the components on a network to allow multiple
users to simultaneously share the same resources regardless of physical
location. Examples: Novell NetWare, Windows Server, Banyan VINES
 Operating systems
 Firewall: - a piece of hardware or software put on the network to prevent
some communications forbidden by the network policy.[12] A firewall
typically establishes a barrier between a trusted, secure internal network
and another outside network, such as the Internet, that is assumed to not
be secure or trusted
 Network security applications
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12.  Network Services:
 DSL: is a family of technologies that are used to
transmit digital data over telephone lines
 Satellite
 Wireless protocols
 IP addressing
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13.  What is Bandwidth: the rate of data transfer, bit rate or throughput,
measured in bits per second (bit/s)
 What is Bandwidth throttling: - This is a purposeful slowing of available
bandwidth
 Why throttling?
 An ISP might throttle bandwidth during certain times of the day to decrease
congestion over their network, which lowers the amount of data they have to
process at once, saving them the need to buy more and faster equipment to
handle Internet traffic at that level.
 While very controversial, ISPs also sometimes throttle bandwidth only when
the traffic on the network is of a certain kind or from a certain website. For
example, an ISP might throttle the bandwidth of a user only when heavy
amounts of data is being downloaded from Netflix or uploaded to a torrent
website.
 Sometimes, too, an ISP will throttle all types of traffic for a user after a
certain threshold has been reached.
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14. How do I tell if my bandwidth is being throttled?
If you suspect that your ISP is throttling bandwidth because you've been
reaching a monthly threshold, an Internet speed test done several times
throughout the month might shed light on that. If your bandwidth suddenly
decreases near the end of the month then this might be happening.
Examples: -
http://www.speedtest.net
http://speedtest.kenet.or.ke
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15. Is There a Way to Avoid Bandwidth Throttling?
Virtual Private Network services are sometimes helpful to circumvent bandwidth
throttling, especially if it's your ISP that's doing it.
VPN services hide the kind of traffic that's flowing between your network at
home and the rest of the Internet. So, for example, on a VPN, your 10 hour per
day Netflix binge watching that used to get your connection throttled now doesn't
look like Netflix to your ISP.
Any local bandwidth throttling by your network administrators at work are less
avoidable, if not impossible, most likely because you also probably aren't allowed
to use a VPN service, which requires making certain changes to your computer.
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16. Network connectivity and access
Network troubleshooting tools are a necessity for every network administrator.
These includes the following: -
Ping: - This utility is used to provide a basic connectivity test between the
requesting host and a destination host. This is done by using the Internet Control
Message Protocol (ICMP) which has the ability to send an echo packet to a
destination host and a mechanism to listen for a response from this host. Simply
stated, if the requesting host receives a response from the destination host, this
host is reachable.
Tracert/traceroute: - used to determine more specific information about the
path to the destination host including the route the packet takes and the response
time of these intermediate hosts.
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17.  Ipconfig/ifconfig: - shows the IP configuration information of a device
 Nslookup: - used to lookup the specific IP address(es) associated with a
domain name. If this utility is unable to resolve this information, there is a
DNS issue
 Nestat: - current state of the active network connections on a host
 Pathping/mtr: - In an effort to take advantage of the benefits of both the ping
and tracert/traceroute commands, the pathping and mtr utilities were
developed.
 Route: - utility is used to display the current status of the routing table on a
host.
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