Wednesday, 26 August 2015

Client/Server Systems Development - Service & Support

Contents:

System Administration
Network Management
Client/Server Systems Development Training

System Administration

We have to ensure that the client/server hardware are to the organizational standards and tested prior to implementation. Softwares should be installed according to standards and works with trained people. This is the first phase of the success of a client/server applications.

Availability

Availability means system, the system availability for processing data and doing its expected work whenever needed. Minicomputer and mainframe data centers provide atleast 99.8 percent availability with today's technology.

To achieve this level of availability, a combination of technological and procedural steps are followed. Most availability failure is due to human error. To reduce this, data centers implement rigid procedures to manage.

Whether the change is hardware, network,system or application software, stringent procedures to request, validate,test and implement the change are defined and adhered. Backout procedures are defined and tested to ensure that if a failure occurs after implementation of the change, the data center can fall back to its previous status.

Technological features such as separate electrical power sources, backup and battery power sources, redundant processors and disk devices all are used to ensure that failure of a single component will not take down the data center.

Data centers use highly skilled professionals in the central location. They are expected to be able to recover the site quickly after any failure.

Reliability

Reliability requires applications to be protected from overwriting each other and requires shared memory to be accessed only by authorized tasks.

Security must be implemented to allow access to resources only by authorized users. The software must automatically handle multiple user contention, provide full recovery after failure of in-flight updates, and provide utility functions to recover a damagedd magnetic disk.

Serviceability

Products based on standard protocols such as the Simple Network Management Protocol (SNMP) provide the necessary feedback of event alerts to support the remote systems management function. It is necessary that the architecture design take into account the issues of standards and products to be serviceable.

Performance

In the centralized minicomputer and mainframe environment, trained technical support personnel and operations staff monitor performance on an ongoing basics. Sophisticated monitoring tools, track the system's day-to-day performance. If trends show performance degrading, systems managers can add hardware or make adjustments to improve performance before it affects the use community. Additional tools are available to simulate new applications before they move into production. This means that the organization learns in advance the resource requirements of new applications. Changes can be made to the operating environment to ensure that performance will be acceptable.

In the client/server environment, neither UNIX, Windows NT, nor OS/2 yet provides these sophisticated performance monitoring tools.

Network Management

Network management involves active and passive monitoring of network resources for the purpose of troubleshooting, detecting potential problems, improving performance, documentation and reporting. A diversity of management applications and protocols are available. The network administrator, working at a management console, produces reports and graphs about the state of the network from this information. Agents may also provide alerts that warn of problems of performance degradations. Most management applications of this type are built around the internet's SNMP.

Desktop management software to remotely manage client systems and control desktops. Software installation, updating and licensing to automatically install or update software over a network and ensure that an organization is within its usage license. Network asset management to track hardware and software inventories. Help desk management to provide user assistance over the network. Network protocol analysis Hub and router management Network design, capacity planning and simulation software.

One of the problems with network management is that most enterprise networks consist of a wide variety of computer platforms, network topologies, communication protocols, operating systems and applications. Therefore, the network itself is often used to extend the reach of the network administrator by single remote monitoring and control tools.

Remote Systems Management

LAN administrator should be able to connect remotely to and then manage the workstation of any user who has problem.

Security

Security is  all about protecting data and data streams. Physical security techniques are fairly straightforward- you lock things up in secure rooms. Software security includes user logon, authentication, authorization and access controls.

Client server systems development training

Client/Server computing provides an opportunity to reengineer the business process by using technology earlier and in a more integrated manner. It does not eliminate the need to train for the new process.

Training advantages of GUI applications 

A major training benefit of the graphical user interface GUI is the opportunity to provide an intuitive interface. Each time standard functions are used in a GUI platform, thhey are invoked in the same way.

Components of Client/Server Applications - Connectivity

Contents:

Open System Interconnect (OSI)
Inter Process Communications
Communications Interface Technology
Wide Area Network Technologies
Client/Server Systems development software
Client/Server development methodolgy
Client/Server System Development Hardware
Level Processing Units

Components of Client/Server Applications - The Server


Contents:

Role of the server
Server Functions
Network Operating System
The Server Operating System
System Application Architecture (SAA)


A Server is a network connected computer system that provides services to network users. Most large companies have banks of relatively inexpensive computers that operate as file servers, application servers, database servers, e-mail gateways and communication servers. These systems run network operating system.

The "new" server is often a scalable system into which additional processors and other components may be added at any time. Such systems are platforms for future expansion and growth. They provide centralized services to support the new class of network computers and Net PCs.

Clustered systems protect against the loss of any one system. Data is stored in separate fully redundant arrays than any server can access. The system can be scaled by simply adding more servers. A simple application can also be run across the cluster and all the servers are used as a single processor.

A typical intel-based multiprocessor system has four processors. To take advantage of this system, you will need an operating system that supports SMP (Symmetrical Multiprocessing)
eg: Windows NT, Novell

An SMP system breaks processing tasks into separate threads and each thread is processed by a separate CPU. Thus, a four processor system could theoretically complete a task four times faster than a single-processor system. SMP systems implement shared memory, disk storage and other system features.

Role of the Server

Servers provide application, file, database, print, fax, image, communications, security, systems and network management services.

An application server is a machine that serves as a host replacement. For client/server applications that are classified as host-based, the host is the server to the GUI - based clients.

File servers mange a work group's applications and data files. So that they may be shared by the group. File servers are very I/O oriented. File locking is handled by locking the entire file or by locking byte ranges.

Two techniques used to minimize the amount of data that passes over the network are:

  • organizing data so that the data needed by a particular application request is stored in a single contiguous block.
  • storing copies of data accessed by more than one user to help with concurrency problems.
Database server is the most typical use of server technology in client/server applications. Data base servers can have a lock manager, multi-user cache management and scheduling and thus have no need for redundant data.

Database and data/compute servers improve request handling by processing a SQL client request and sending back to the client only the data that satisfies the request.

Print servers provide support to receive client documents, queue them for printing, prioritize them, and execute the specific print driver logic required for the selected printer.

Fax servers provide support similar to that provided by print server. The fax server must be capable of dynamically compressing and decompressing documents for distribution, printing and display.

Image servers operate in a manner similar to fax server. Communication servers provide gateways to other LAN's, networks, mid range computers and mainframes.

Server Functions

The term server has two general connotations:
  1. A piece of hardware that provides shared services in a networked environment.
  2. A software component that provides a generalized functional service to other software components.
File Services

File Services handle access to the virtual directories and files located on the client workstation operating environment. The file services provide this support to the remote server processor.

Print Services

  • The server can manage several printers.
  • The server can keep track of special paper.
  • Print jobs can be scheduled to run at regular intervals.
  • The server can restart the job from its spool file without asking the user to re-enter the print request.
  • Access to printers can be both extended and restricted.
The same as printer services is fax services and image services.

Database Services

Client/Server database engines such as Sybase, IBM's Database Manager, Ingress, Oracle and Informix provide support at the server to execute SQL requests issued from the client workstation. The file services are still used for space allocation and basic directory services, but all other services are provided directly by the database server. Relational database management systems are the current technology for data management.
  • Flat Files: In 1960s flat files is used in database technology through the media like punched cards and disk files.
  • Hierarchical Databases: The next generation of database technology is the hierarchical database which could store related record types physically or logically next to each other. o The disadvantage is that only applications that access data according to its physical storage sequence benefit from locality of reference.
  • Relational Database: This technology provides the current data management solution to many of the problems inherent in the flat-file and hierarchical technologies. Many database engines were used in the client/server technology. Many features are included in the database engines.
    1. Performance optimization tools.
    2. Dynamic transaction back out.
    3. Roll back transaction back out.
    4. Audit File Recovery.
    5. Automatic error detection and recovery.
    6. File reclamation and repair tools.
    7. Support for mirrored databases.
    8. Capability to split database physical disk drives.
    9. Remote distributed database management features.
    10. Maintenance of accurate and duplicate audit files on any LAN node.
    11. Locking mechanisms to guarantee data integrity.
    12. Deadlock detection and prevention.
    13. Multi threaded application processing.
    14. User access to multiple databases on multiple services.
  • Object Oriented Databases: Object Oriented Databases are designed for the nested structure. The object model supports browsing of object class libraries, which allows the reuse, rather than the reinvention of commonly used data elements. Objects in an object oriented survive multiple sessions, they are persistent. OODBS can issue a single message that contains multiple transactions. Object oriented databases are favored for applications where the relationships among elements in the database carry the key information. Object oriented models capture the structure of the data.

Network Operating System

Network operating system provide features for controlling LANs and internet works and for serving clients. A NOS provides a set of protocols for accepting requests from clients and responding to those requests. A NOS also provides a shared file system and set of security features and controls to control user access to network resources.
  1. Novell Netware
  2. LAN Manager
  3. Banyan's VINES
  4. PC Network File Services (NFS)
The features of NOS are:
  • Services provided such as virus checking, software distribution, software and hardware inventory, ans server to server application.
  • OS features such as support for SMP (Symmetrical Multiprocessing), processor support, protocol support and automatic hardware detection.
  • File and print service features.
  • Fault tolerance features such as clustering, RAID and backup services.
  • Security features such as authentication, authorization, logon restrictions and access controls.
  • Support for name and deliver services.
  • Management, administration and auditing features.
  • Internet working, routing and WAN support.
  • Client OS support and support for remote dial-up users.
Novell Netware

Novell Netware is a network operating system that works on LDAP principles to offer users a robust platform for hosting files, printers and other network related services.
  • Early design in 1983
  • Designed to host files to DOS workstations
  • First OS to use Network Drive Mapping to local workstations
  • Propriety designer of the IPX Network Interface
  • Originally manufactured by the Superset Corporation bought by Novell in 1983 to support a network OS for the hardware Novell was making at the time.
With the introduction of Netware 5 Novell offers its users and administrators a never before seen level off server management. Meaning that the majority of all work can be done without directly accessing the server through console 1 or Novell's IManager Software.

LAN Manager

Microsoft LAN Manager is a network operating system that run on Microsoft's version of OS/2. The product was also marketed by IBM as IBM LAN Server. Both products have been superseded by new products. In the case of Microsoft, LAN Manager was replaced by Windows NT Server, a self sufficient operating system that does not require OS/2. In the case if IBM, LAN  Server was replaced with OS/2 warp Server. Windows NT server maintains compatibility with servers running LAN Manager. It also includes many of the features that were in the original LAN Manager product. 

Banyan VINES

Banyan VINES is a networking operating system with a UNIX Kernel that allows users of popular PC desktop OSs such as DOS, OS/2, Windows, and those for Macintosh Systems to share information and resources with each other and with host computing systems. VINES first appeared in the 1980s. It provides full UNIX NFS (Network File System) support in its core services and TCP/IP for transport. It also includes Banyan's Street Talk Directory Services, possibly the most popular component of the operating system.

VINES features:
  • built around servers that provide services to client workstations. 
  • designed to help organizations build fully distributed computing environments around a suite of enterprise network services including security, messaging, administration host connectivity and wide area network communication.
  • provides enterprise network services that are not server-centric but services-centric
Banyan Street Talk allows VINES users to quickly find and access all resources regardless of where they reside in the enterprise. Banyan's Street Talk Director Service is designed to integrate and manage a growing variety of heterogeneous environments including Banyan networks, Windows NT, UNIX and Netware. Street Talk Directory Assistance provides distributed directory services.

VINES support a wide range of messaging capabilities. VINES establishes a framework for highly scalable, standards based SNMP (Simple Network Management Protocol) management, allowing administrators to cost effectively manage the network from any point.

VINES runs on an Intel-based processor system and supports Ethernet, Token Ring or FDDI (Fiber Distributed Data Interface) network adapters. It support popular clients including DOS, OS/2, Windows and Macintosh. The package comes on CD-ROM with licenses for 100, 250, 500 and 1,000 users.

PC Network File Services (NFS)

NFS is the standard file system support for UNIX. PC NFS is available from SunSelct and FTP to provide file services support from a UNIX server to Windows, OS/2, Mac and UNIX clients.

NFS lets a client mount on NFS host's filing system as an extension of its own resources. SunSelect includes instructions for adding PC NFS to an existing LAN manager or Windows for workgroups network using Network Driver Interface Specification (NDIS) drivers.

With the increasing use of UNIX Servers for application and database services, there is an increase realization that PC NFS may be all that is required for NOS support for many workgroups. This can be a low-cost and low maintenance option because the UNIX Server is easily visible from a remote location.

The Server Operating System

Servers provide the platform for application, database and communication services. The OS platforms that have the greatest potential and are prevalent today are:
  1. Novell Netware
  2. OS/2
  3. Windows NT
  4. MVS
  5. VMS
  6. UNIX

Novell Netware

Netware is used by many organizations, large and small, for the provision for file, printer and network services. Netware is a self-contained operating system.

Novell has three primary network operating systems. They are:

  1. Novell Netware 4.11: A high end network operating system that includes NDS (Novell Directory Services) and SFT (System Fault tolerance) features that guard against downtime by integrating two physically separate servers.
  2. Novell intranetware: An intranet platform product that has all the features of Netware 4.11.
  3. Novell Netware 3.12: Novell traditional Netware Operating System without NDS, SFT and intranet features.
Netware 4.11 is an NSE (Network Services Engine) that provide a wide range of built in services, including directory services, security, routing, messaging, management, file and print services and TCP/IP support. It also provides a platform for expanded services such as telephony, multimedia services, internet and intranet browsing and publishing and more.

OS/2

OS/2 is IBM's 32bit desktop OS that runs on Intel processors. A server version is called OS/2 warp server.

The current version of OS/2 includes voice recognition software, internet access and peer-to-peer network support. Networking services include support for the TCP/IP protocols and internet protocols such as Telnet, Gopher and FTP. The peer-to-peer network services in OS/2 let users easily share resources such as files, printers and modems with other OS/2 users or with other network servers such as OS/2 LAN Server, Microsoft Windows for Workgroups, Microsoft Windows NT, Microsoft Wnidows 95, Microsoft LAN Manager 2.x and Artisoft LAN tastic6.0.

OS/2 also supports Novell Directory Services, which allows OS/2 users to access resources globally across an organization without having to know exactly which Netware server contains the information.The OS also includes IBM personal communications/3270, a communication package that lets users connect with IBM SNA (Systems Network Architecture) systems over TCP/IP networks.

A remote access dial up service feature lets telecommuters and mobile workers connect to the network resources at the home office networks.

Windows

  • Graphical User Interface
  • Multitasking capabilities
  • Full-featured OS for desktop users and network server application.
Windows CE

  • a "small foot print" OS
  • designed for specialized computing devices
  • handheld PCs, telephone, television sets
Windows 95

  • 32 bit desktop OS
  • scalable
  • performance improve when memory is increased
  • built in networking, fax, electronic messaging, internet accss software, mobile computing support and support for DOS applications.
Windows 98

  • Fully integrated with internet/web technologies
  • Support new multimedia hardware technologies and entertainment platforms
Windows NT Workstation 4.0

  • High end desktop OS
  • Powerful 32 bit and high end performance
  • Provide very high level of security, reliability, manageability, networking and performance
Windows NT Server 4.0

  • 32 bit modular architecture
  • Flat address space
  • Processor support
  • Preemptive multitasking
  • Multithreading
  • Network and distributed computing support
  • Internet and web support
  • Future enhancement
MVS (Multiple Virtual Storage)

  • Primary OS in 1974 for IBM mainframes 
  • Batch oriented
  • Run on IBM S/390 and ES/9000 series computer
  • Provides powerful database server using DB2 and LU 6.2
  • Sybase provide high performance static SQL support
Open VMS

  • DEC mutiuser OS that supports Digital's VAX and Alpha Series computers
  • Open software environment that includes networking support, distributed computing support and multiprocessing
  • Effective database server for client/server applications- RDB, Sybase, Oracle etc.
UNIX

  • Developed at AT & T Bell Laboratories by Ken Thompson and Dennis Ritchie.
  • UNIX comes from UNICS (Uniplexed Information and Computer System)
  • Highly Portable
  • Digital UNIX OS is a 64 bit advanced kernel architecture
  • Sun Microsystem's solaris is the most popular UNIX system.
  • Linux is another free UNIX like OS that runs on a variety of platforms
Features include
  • Multiuser system that supports networking and distributed file systems such as NFS (Network File System) and AFS (Andrew File System)
  • Interact with the OS through shell such as Bourne shell, C shell and the Korn Shell
  • Hierarchical file system
  • Unix and the TCP/IP protocols are closely linked.
UNIX provides in one package the ability to install a powerful OS on a computer that lets users share files and run programs on other user's computers through one of the most common and powerful networking protocols in the industry.

Distributed Computing Environment

Distributed computing is basically client/server computing on a wide scale. Data is not located in one server, but in many servers, and these servers might be at geographically diverse areas, connected by WAN links into enterprise networks that join the many formerly autonomous computer systems in workgroups, departments, branches and divisions of an organization.
  • Networks built with web technologies
  • Support access to data already located at diverse sites
  • Provides protection from local disasters
The components needed for the distributed environment includes
  1. The network platform that supports a variety of multivendor products and communication protocols necessary to link those systems.
  2. Application interfaces that let users make requests to servers using real-time connection oriented methods or message passing systems.
  3. A directory naming service that keeps track of resources and information and where they are located.
  4. A time service to synchronize events among servers that hold related information.
  5. DBMS that support partitioning and replication
  6. A distributed file system that operates in a peer-to-peer mode to allow users working at workstations to act as both clients and servers.
  7. Security features such as authentication and authorization.

Systems Application Architecture (SAA)

SAA is a set of application and user-interface specification for IBM Mainframe OSs. There are three main components in the architecture.
  1. Common Programming Interface (CPI): It provides a common environment across the SAA platforms for executing programs.
  2. Common User Access (CUA): Defines how information is presented to the user using an interface that is common over different platforms.
  3. Common Communication Support (CCS): Defines the interconnection of SAA systems and the protocols used for communications and data exchange.
SAA is a failed strategy because it only linked IBM systems. The open BluePrint is IBM's newest vision that encompasses support for multiple application interfaces, networking protocols and transmission methods such as frame relay and ATM.