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Vs Multi-user client / server applications
There is no denying the fact that the server is a multi-user computer, where there are no unusual hardware condition converts a PC into a server and as such, the hardware platform should be preferred on the basis of the demand for applications and financial rigor. Customer Application Servers / Server beaten work when configured with an operating system compatible with shared memory, application isolation, and preemptive multitasking. An operating system preemptive multitasking allows a higher priority task to preempt or take control of a processor is currently running, lower priority. The server provides and controls shared access to server resources. Applications on a server should be isolated from each other so that an error in one can not harm another. Preemptive multitasking ensures that task alone can not handle all the server resources and other tasks thwart the service. There should be a means to define the relative priority of tasks on the server. These requirements are specific to the client / server and can not get the implementation of the file server. Because the file servers running only the unique task of file serving, can operate in a more limited operating environment without the need for isolation and preemptive multitasking applications.
The conventional minicomputer and mainframe hosts have acted as de facto corporate servers for the network of terminals that support. Because the functionality is only available user terminals is through the host, personal productivity data, as well as business information systems are stored on this server host. Services network, application services and database services are provided centrally from the host server. Many organizations in downloading data from corporate servers legacy for the handling of local jobs. In the client / server, the server definition will include these functions, perhaps even implemented in the same or similar platforms. Moreover, the advent of open systems-based servers is to facilitate the placement of services on different platforms. Client / Server is a phenomenon that developed from the beginning. remote working groups have had to share expensive resources and have their workstations connected desktop local area networks LAN has grown until they are widespread in the organization. However, often are isolated from each other. Many organizations have integrated the functionality of their dumb terminals on their desktop workstations to support in text mode, host-based applications of the workstation. The following wave of client / server computing is happening now, as the organizations of the mid-1990 will begin to use the cheaper and more available power processing workstation as part of your business systems. The Novell network operating system (NOS), NetWare, is the most widely installed LAN. It provides the main file and print server supports. However, a limitation of NetWare client needs reliable / server has been the requirement for a period additional processor runs as a separate database server. The availability of database server software companies like Sybase and Oracle to run on the server NetWare is spreading plate this limitation.
Speaking of roles, servers provide application, file, database, print, fax, image, communications, security, network and systems management services. These are each described in some detail in the following sections. It is important to understand that a server is a concept architecture, not an explanation of physical implementation. Client and server functions can be provided by the same physical device. With the movement toward peer computing, each device potentially operate as a client and the server in response to requests for service. Application servers provide functionality business to support the operation of the client workstation. In the client / server model of these services can be provided for full or partial business function invoked through an inter-process communication (IPC) service request. Any requests based RPC messages can be used. A collection of servers applications can work together to provide a business function. For example, a payroll system may be the employee information managed by a application server, earnings calculated by another application server, and deductions calculated by a third party application server. These servers can run different operating systems on different hardware platforms and can use different database servers. The client application calls these services regardless of technology or geographic location of different servers. Object technology provides the technical basis for the application server, and the widespread acceptance of the CORBA standards to ensure the viability of this trend. File servers provide data at the record level of services to any database application. Space required for memory storage is allocated, and free space is managed by the file server.
catalog functions are provided by the file server for compatibility with file names and directory structure. File name maximum length of 8 to 256 characters, depending on the particular server operating system support. programs stored are usually loaded from a file server to run on a client or host server platform. Database servers are managed by a database engine such as Sybase, IBM, Ingres, Informix, Oracle o. The file server provides the initial space and the database engine allocates space for tables in the space provided by the file server. These hosting services are responsible for providing specialized data services required of a product failure database and automatic energy recovery, hardware, or software, management of space within the file, the reorganization of databases, record locking, the deadlock detection and management. The print servers support clients to receive the documents queued for printing, to prioritize them, and run the logic of the specific printer driver required for the selected printer. The print server software must have the necessary logic to support unique characteristics of each printer. Effective support print server include error recovery and congestion notification of operator error with instructions to reboot. fax servers provide similar support to that provided by print servers. Furthermore, fax server queue outgoing faxes for distribution to communications charges are lower. Since faxes are distributed in compressed form, using the Group III or Group IV compression the fax server must be able to compress and decompress documents dynamically for distribution, printing and presentation. This operation is usually performed by the addition of a fax card in the server. If fax is rare, the software support for compression and decompression of options can be used. Servers Image work similar to fax servers.
Infrastructure servers provide support for wide area network (WAN) communications. This support usually includes support for a subset of IBM System Network Architecture (SNA), asynchronous protocols, X.25, ISDN, TCP / IP, OSI, and LAN-to-LAN communications protocols NetBIOS. In the implementation of Novell NetWare, Gateway Communications offers a product leader in communications. In the LAN Server and LAN Manager environments, OS / 2 server products communications are available on IBM and DCA. In the Banyan VINES environment, the addition of DCA for VINES provides support for SNA connectivity. UNIX servers provide a product range of accessories from various vendors to support the full range of communications needs. decent support VMS servers, TCP / IP and SNA as well as various asynchronous and serial communication protocols. MVS servers provide support for SNA, TCP / IP, and some support for other types of asynchronous communication. Restricts Server Security access to access programs and data from the server. Communications access is controlled from the communications server. In most implementations, the use of a session User ID is the primary means of security. Using the LAN server, some organizations have implemented integrated access the answer / Control Facility (RACF) security through the creation of profiles in the MVS environment and unloading of the LAN server for domain control. Systems and network management services for the local LAN are controlled by a LAN administrator, WAN, but the services must be provided by a central site. In general, the remote LAN management is carried out from the center site central database by trained MIS. The discussion in the following sections describe more specifically the functions provided by the server in a NOS environment. Applications is issued by a client for the NOS software resident on the client computer services. These services format of the application in a case of RPC and send the request to the application layer the client protocol stack. This request is received by the application layer protocol stack on the server. File services manage access to virtual directories and files that are on the client workstation and the permanent storage server. These services are provided through the redirection software out as part the client workstation operating environment.
To reduce the effort and the effect of the installation and maintenance of software, the software must be loaded from the server for execution on the client. New versions can be updated on the server and immediately available to all users. In addition, the facility in a location core reduces the effort needed for each workstation user control of the facility. Because each user of client workstation uses the same installation software, optional parameters are consistent, and help desk operators are aware of them remotely. This simplifies the analysis that must occur to provide support. The exchange of information, such as text documents, it is easier when everyone is at the level of delivery and uses the same default settings in the same software. Central services productivity, such as style sheets and macros can be configured for general use. Most personal productivity products allow local parameters such as colors, default printers, and so on locally established as well. Backup server can be programmed and supervised by a trained support person. Backups of client workstations can be scheduled from the server, and data can be stored on the server facilitate recovery. Tape or optical backup units are typically used for backup, these devices can easily provide support for many users. The placement of the server and your backup in a safe place to help prevent theft or accidental destruction of backup. A central location is easily controlled by a support person to ensure that the functions of backup is complete. With more organizations looking at the multimedia and imaging technology, large optical storage devices are most appropriately implemented as shared servers. high quality printers, faxes generated for workstations and plotters are natural candidates to support a shared server. The server can accept input from many customers, the queue according to priority of the request and handle it when the device available. Many organizations obtain substantial savings by allowing users to generate output fax your workstations and tail in a fax server for transmission when communication costs are lower. Incoming faxes can be queued on the server and transmitted to the appropriate client either on receipt or on request. In coordination techniques with workflow management, images can be captured and distributed to the appropriate client workstation in the image server. In the client / server model, work queues on a server maintained by a supervisor in concert with the default algorithms that determine how to distribute the work queue. mail incoming paper can be converted into image form in the mail room and sent to the appropriate client through LAN not through internal mail. capture and distribution Images can be centralized indexing center. This index can be maintained by the database services to all authorized users to query. Thus, a Once the images are captured and available for immediate distribution to all authorized users. well-defined rules for electronic document management allow this technology to fully integrate into the desktop work environment. There are opportunities for dramatic cost savings and efficiency gains if proper technology application and use. Article 10 explains in more detail the issues of electronic document management.
In database servers data first hours were actually file servers with a different interface. Products such as dBase, Clipper, FoxPro, and Paradox to run the database engine primarily on the client machine and use file services provided by the file server to record, access and management of free space. These are new and more powerful applications original models with flat file indices extracted directly accessing the registry. exchange control is administered by the application program, which issues requests lock and lock controls, and the database server, creating a table of locks that will be questioned every time a record lock check access generates. Since access is at the record level, all records that meet the primary key must be returned to the client workstation for filtering. There are no facilities procedure to run code on the server, running together, or to filter the rows before returning to the workstation. This lack of capacity increases dramatically the likelihood of records that are locked when multiple clients access the same database and network traffic increases when the unnecessary rows are returned to the station work only to be rejected. The lack of logic execution server prevents these products to provide automatic updating of priming and partial recovery after an application, system or hardware failure. For this reason, systems that operate in this environment requires a support system programmer with experience to help in recovery after a failure. When applications are simple and require only a single row to be updated at each interaction, this issue recovery does not arise. However, many client / server applications are required to update more than a single row, as part of a logical unit of work. Client / server database engines as Sybase, IBM Database Manager, Ingres, Oracle and Informix support to run the server application requests came SERVER the client workstation. File services are still used for the allocation of space and basic services directory, but all other services are provided directly by the database server. Management systems relational databases are current technology for data management. The main disadvantage the hierarchical technique is that only applications that access data according to their physical benefit stream storage locality of reference. Changes on the requirements of applications that require a different approach to data access require reorganization. This process, which consists of reading, sorting and re-enter the base data into a new sequence, not transparent to applications that are based on original physics sequence. The indices that provide direct access to the database provided the ability to view and access to information in a sequence different from the physical sequence. However, these rates should be known by the user at the time of application develops. The developer explicitly index references to get to the data of interest. Therefore, rates can not add more without changing any programs that need such access to use the index directly. The indices can not be removed without changing the programs that currently access to the index. Most implementations require application developers to be sensitive to the organization and the appearance of the columns within the record. Therefore, the columns can not be added or removed without having to change any programs that are sensitive to these records. Application of sensitivity to physical implementation is the main problem systems with hierarchical database. Application of the sensitivity of physical storage is one of considerable complexity in navigation and programmers applications go through the hierarchy in search of their desired data. Attempts by the database providers to improve performance have generally increased the complexity of access. If life is too easy today, try to create a bidirectional virtually paired logical relationship IMS, so the companies that use products like IMS IDMS and usually have highly paid personal database of technical support. As hardware technology evolves, it is important for data management capabilities to evolve to use the new capabilities. Technology relational database management solution provides current data for many of the problems inherent a flat file technologies and hierarchical. In the late 1970s and early 1980s, products such as Software AG Adabas and 2000 system were introduced in an attempt to provide application flexibility required by the systems of the day. IBM IMS and IDMS network Cull tried to add features to their products to increase this flexibility. The relational products were first introduced by Dotcom ADR with DB and Computer Corporation of America Model 204. Each of these implementations extracted indices used direct access to stored data without having to navigate the database or flat file classification. All products tried to keep some of the performance benefits offered by the locality of reference (columns and records storage as close as possible to the primary column and register).
The development of a relational algebra which defines the operations that can be made between the tables has an efficient implementation of the RDBMS. The establishment of industry standards for defining and access to relational tables has accelerated the acceptance of RDBMS as the de facto standard for all clients / today's server applications. Similar rules does not yet exist for OODBMSs. There is a place for both models. To be widely used, OODBMSs need to integrate seamlessly with RDBMS technology. Table 4.1 compares the terminology used by RDBMS and OODBMS proponents. Relational databases are characterized by a simple data structure. All access to data and relationships between tables are based on values. A state data value is determined solely by the concatenation of the table name, column name and the value of the unique identifier of the row (primary key). Relationships between tables are determined by a common occurrence of primary key values. Applications to build a vision of information in the tables by a combination based on common values. The result of the combination is another table that contains a combination of column values tables involved in the club together. There are some applications for which RDBMS have not achieved acceptable performance. Primarily, these are applications that require very complex data structures. Thousands of tables can be defined with many relationships between them. Often, the rows are sparsely populated, and applications often require many rows to be linked, often recursively to produce the necessary perspective. The main suppliers in this market are the objectivity Inc., works of design, and Versant. Other vendors HP, Borland, and the input objects have incorporated features into their products. The application features that lead to an election are shown in OODBMS Figure 4.3. OODBMS production will become suitable for these applications with the introduction of 16Mbps D-RAM and the establishment of persistent (permanent) bases D-RAM data. Only those functions will be your actual use of I / O. Periodically, databases D-RAM backup actual magnetic disk or optical storage. During 1993, a significant number of production applications OODBMS were carried out. With the confidence and experience gained in these applications, the momentum is building, and in 1994 and 1995 will see a significant increase in the use of OODBMSs for business-critical applications. OODBMSs have reached a level of maturity that matches the demand for multimedia enabled applications. The complexity of dealing with the demands of the multimedia features of OODBMS effective storage and handling.
Client Applications / Server requires LAN and WAN communication services. LAN's basic services are an integral part of the NOS. WAN services are provided by various communications server products. Article 5 provides a full discussion of the problems of connectivity to the client / server model. Client / server applications require similar security services to those provided by host environments. All users should be required to log on with a user ID and password. If the passwords may be visible to unauthorized users, the firewall must insist that passwords are changed regularly. The company at the table means that a logon ID and unique The logon sequence is used to obtain the authority once to access all the information and the process so that the user has a need and right of access. Given that data can be stored in a physically less secure area, the option must exist to store data in encrypted form. A combination of identifying username and password should be required to decrypt the data. The new options, such as less flexible workstation with the standard built-in data encryption (DES) coprocessors are available from vendors such as Computer Company Beaver. These products automatically encrypt or decrypt data written or read from the disk or communication line. The encryption and decryption are done using the DES algorithm and password. This ensures that no unauthorized user can access to stored data or data communications. This type of security is especially useful for portable computers involved in client / server applications, as laptops do not operate in an environment with the same physical safety of an office. To access the system from a laptop without using a PIN correctly and password would be courting disaster. NetWare is a family of LAN products with support for IBM PC and Apple Macintosh and IBM-PC clients compatible servers. NetWare NOS is a property in the literal sense of not requiring another operating system like DOS, Windows, Windows NT, OS / 2, Mac System 7, or to run on a UNIX server. A separate Novell NetWare UNIX portable products provide server support for implementations of UNIX RISC-based leaders, the IBM PC-compatible systems with Windows NT, OS / 2, high-end Apple Macs running Mac System 7, and Digital Equipment Corporation VAXs running VMS. NetWare provides the main LAN environment to share files and printer resources. He had 62 percent market share in 1993. In general, the product is installed as standard in many organizations.
Suffice to say that LAN Manager and from IBM, LAN Server, are standard products for use in client / server implementations using OS / 2 as the server operating system. LAN Manager / X is the standard product for client / server implementations using UNIX System V as the server operating system. Microsoft launched its advanced products Windows NT server in the third quarter of 1993. During 1994, would be enhanced with the support of network management services of Microsoft, now called "Hermes" and network services company Banyan (ENS). Advanced Server is the natural migration path for existing Microsoft LAN Manager and IBM LAN Server customers. Existing LAN Manager / X customers Advanced Server probably will not find an answer to your dreams before 1995. AT & T has assumed responsibility for the LAN Manager / X version. Vendors such as Hewlett-Packard (HP) have reluctance of AT & T products AT & T and Microsoft has an agreement to keep the API compatible with all basic functions. Advanced Server and LAN Manager provides client support for DOS, Windows, Windows NT, OS / 2, 7 and Mac system. Server support extends to NetWare, AppleTalk, UNIX, Windows NT and OS / 2. client workstations can access data from both NetWare and LAN Manager servers at the same time. LAN Manager supports NetBIOS and Named Pipes LAN communications between clients and servers OS / 2. redirection services are provided to map files and printers on remote workstations for customer use. Advanced Server also supports the TCP / IP. In early 1994, Advanced Server product will remain a young man with many missing pieces. Even more competitive annoying Microsoft and Novell is delaying the release of NetWare client software applicant and Core Protocol (NCP) support. Microsoft has added support TCP / IP for LAN Manager 2.1 and Advanced Server, with Net View and Simple Network Management Protocol (SNMP) agents. Therefore, the tools are in place to facilitate remote LAN management for local area networks LAN Manager. Microsoft has announced support for IBM Net Vista 6000 advanced server management.
Advanced Server provides integrated support for the processing of peer-to-peer and client / server applications. Existing support for Windows NT, OS / 2, UNIX and Mac System 7 allows application clients, database and communication servers running on the same machine as the file and print server. This feature is attractive in small LANs. Support Native preemptive multitasking operating system and storage protection ensures that these server applications do not reduce the reliability of other services. Although Windows NT is launched to provide the database, applications and communications services for client / server applications, using Novell as NOS LAN of choice continue for peripheral resources sharing applications. Microsoft has tried to anticipate the market for small LAN with Windows for Workgroups product. This attacks the same market NetWare Lite with a low cost product that is tightly integrated with Windows. It is an attractive option for small organizations without a requirement for large networks local area. The complexity of management systems become less attractive in a business environment and are using Novell. WWW can be used in conjunction with Novell for groups work WFW wish to use some services, such as group scheduling. IBM has signed an agreement to resell and integrate the product of Novell NetWare environments where both IBM LAN Server and Novell NetWare are required. NetWare provides more functional, easier to use and more efficient file and print services. In environments in which they are the only LAN functions, is preferable to NetWare LAN Manager Derivatives. Interconnection capacity with the world SNA makes the product attractive IBM LAN Server organizations that prefer to run both products. Most large organizations have working groups of the department that require only the services offered by Novell well, but you can use the LAN Server for client / server applications using SNA and APPN services. IBM and Microsoft had an agreement for the API of the two products equivalent. However, the dispute between the two companies over Windows 3.x and OS / 2 has ended this cooperation. The latest release of NT LAN Manager 3 and LAN Server 3 are closer to the equivalence of the agreement, but there is no guarantee that this trend will continue. In fact, there is every indication that the products differ with different server operating system is focused for the two companies. IBM has a very attractive price LAN Server so if OS / 2 clients are used, LAN Server a low cost option for small LANs. LAN Server is compatible with DOS, Windows, and customers of OS / 2. No support has been announced for Mac System 7, although it is possible AppleTalk interconnect and local area networks LAN Server to share files and data communication services.
Street Talk allows resources that are identified uniquely in the network, which facilitates access and manage. All resources, including file services, users, and printers, are defined as objects. Each object has Talk Street name associated with it. Speak street names follow a three-level hierarchical format: Item @ Group @ Organization. For example, a user can be identified as Psmith @ @ TNET Cerritos. All network objects are stored in a distributed database that can be accessed worldwide. Novell NDS is similar to Street Talk functionality. However, there are fundamental differences. NDS can partition and replicate the database, which generally improve the performance and reliability. NDS supports X.500 allows for multiple levels of hierarchy. Street Talk is compatible with a fixed hierarchy of three levels. The NDS architecture provides more flexibility, but with the complexity and the corresponding Street Talk is less flexible but less complex to manage. One advantage of the current version of the talk of the street has more than NDS is that objects can have discussion Street unlimited attributes available for selection. Novell and Microsoft have announced support for Banyan ENS into their products to be available in Q2 1994. Banyan and provide DCA SNA services for the VINES environment. VINES support for UNIX, DOS, Windows, OS / 2 and Mac System 7 clients. NFS support is the standard file system of UNIX. PC NFS Sun is available to support Choose and FTP file services from a UNIX to Windows, OS / 2, Mac and UNIX clients. Client / Server requires LAN and WAN topologies to be in place to provide the necessary interface for shared applications and data. Gartner Group 1 respondents and calculated the topologies Microsystems' integration for the period 1986-1996, whose results are shown in Figure 4.6. Of particular interest is the projection that most workstations will be within the LAN 1996, but only 14 percent will be involved in an enterprise LAN that date. This represents a fairly pessimistic for interconnected LAN-to-LAN and connectivity across the enterprise. These figures will probably prove to be underestimated significantly if organizations take an architectural perspective for the selection of their platforms and tools and the use of these tools in an organizational system optimized development environment (SDE). Routers and communication servers are used to provide communication services between LAN and WAN networks in the. In the client / server, these connections will be provided seamlessly with SDE tools. There are implications significant performance if traffic volumes are large. IBM Application APPC LU6.2 and TCP / IP provides the best support high-volume LAN-to-LAN/WAN communications. December DECnet application has always provided an excellent LAN to WAN connectivity. Integrated support for TCP / IP, LU6.2, and IPX provides a solid platform for client / server implementation of DECnet LAN to WAN.
The lack of desktop real estate in most organizations encouraged to move to a single device using terminal emulation of workstation-to access mainframe applications. It will take time and effort before all existing applications based on host in an organization are replaced by client / server applications. In the long run, the host will remain the place of choice for database storage business data and to provide security and network management services. Mainframes are expensive to buy and maintain, difficult to use, inflexible, and large but they provide stability and capacity required by many organizations to manage their businesses. As Figure 4.7 notes, according to International Data Corporation, which will not disappear soon. Its functions will change, but will be around as part of the business infrastructure for many more years. Only organizations that create an architecture strategy and business transformation plans to migrate to client / server in less than a couple of years. Without a good architecture strategy, gradual evolution failure occurs. The information is of value or interest to the whole enterprise must be managed by a data management function and appears to be stored central on each user's desktop. These applications are traditionally implemented as online transaction processing (OLTP) to the mainframe or minicomputer. With the client model / Server, it is feasible to use database technology to replicate or migrate data to distributed servers. Provided that the data resides or is used, the location should be transparent to the user and the developer. The data should be stored in that best suits your business needs. Transaction processing applications are online in sectors such as insurance, finance, government, and sales, all of which produce a large number of transactions. Each of these transactions requires a minimum of you believe that the process time. In these industries, data is often used in the source well informed by the worker. As such, the systems have high availability requirements, data integrity, performance, concurrent access, the potential for growth, security and manageability. Systems implemented in these environments must prove their worth or be rejected by an empowered organization. They must be implemented as part of the work process. OLTP has traditionally been the domain of large mainframe suppliers as IBM and DEC, and special purpose processors, fault tolerance from vendors such as Tandem and Stratus. The client / server model has the capability to provide all services required for OLTP a much lower cost than traditional platforms. All standard client / server requirements for a GUI application portability, client / server partition function, software distribution and development tools are effective for OLTP applications. The first vendor to deliver a quality product production in this area is Solutions Ellipse of cooperation with their product. Before the ellipse, OLTP systems require developers to manage issues integrity processing unit of work, including foreign exchange control and the reversal of transactions. Ellipse offers all the necessary components to build systems with these characteristics. Ellipse currently operates with Windows 3.x, customers of OS / 2 servers and OS / 2 with the database engine from Sybase. Novell is working with solutions port cooperative ellipse as Novell NetWare Loadable Module (NLM). It provides a powerful graphical development environment using a templating language as shorthand for development. This language provides a solid foundation to build an organization SDE and lends itself well to the incorporation of standard components. As UNIX has matured, has added many features found in other commercial systems that operate as VMS and MVS. Currently, there are several offers for OLTP UNIX. IBM CICS is to promote 6000 as a staff reduction strategy for CICS MVS. Database services will be provided by a combination of AIX and MVS.
With the launch Windows NT (New Technology) in September 1993, Microsoft bet its unique position with a server operating system. Microsoft's previous development of OS / 2 with IBM did not create the standard UNIX only alternative was expected. NT provides the services necessary for the functional preemptive multitasking server. Provides excellent support for Windows clients and incorporates storage services necessary protection required for a reliable server operating system. Its application-level security C2 goes beyond that provided by OS / 2 and most implementations of UNIX. Will most of 1994 to obtain the necessary zing applications and to provide a robust industrial strength platform for business critical applications. With the prestige of Microsoft and the marketing muscle, NT will be installed by many organizations such as your server of choice. IBM MVS provides a platform for large applications. Many of the existing application services that organizations have acquired system operating in 370-compatible hardware running MVS. The network environment standard for many large organizations-SNA-is a component of MVS. IBM prefers proprietary tag today under the umbrella of the SAA. The purpose of the AEA is to provide all services on all IBM platforms in a manner compatible with the IBM version of the image of a single system. There is a commitment by IBM to provide support for LAN server runs natively on MVS. This is an attractive option for organizations with large existing investments in applications for MVS. The storage capacity very large data provided by the System 370-compatible platforms with MVS to MVS using LAN services attractive for large organizations. MVS offers a powerful server and DB2 database using LU6.2. With the support of the whole area of LU6.2, applications including DB2 database as part their vision can be issued from a client / server. Products such as Sybase provide high-performance static support Application Server, making this application viable for production applications of high performance. Digital Equipment Corporation provides OpenVMS server as their platform of choice. SLB has a long history in field of distributed computing and includes many of the features needed to act as a server in the client / server model. December was slow to realize the importance of this technology and the company only recently entering the arena as a serious supplier. NetWare servers supports the use of OpenVMS for file services. December offers its own server user interface of a derived product called LAN Manager patchworks. Patchworks run natively on the VAX and Alpha RISC RXP. This is a particular configuration attractive because it allows access to the same processor services to the application, database and file provided by a combination of OpenVMS, NetWare and LAN Manager. Microsoft Digital have announced joint agreements to work together to provide seamless integration of Windows, Windows NT, patchworks, and OpenVMS. This will greatly facilitate the migration OpenVMS client to client / server model. OpenVMS VAX support for database products such as RDB, Sybase, Ingres and Oracle allows this platform to run efficiently as a database server for client / server applications. Many organizations have large investments in hardware VAX and DECnet networking. The option to use these as part of client / server applications is attractive as a way to maximize the value of this investment. DECnet provides support for single system image model. LAN technology is fundamental to the architecture of DECnet. Many large organizations moving to client / server computing world have standardized processing DECnet WAN. For example, Kodak Digital selected as its networking company, even after selecting IBM as its mainframe outsourcing.
UNIX is a key player as a system server in the client / server model. Indeed, the history of UNIX in the field of distributed computing and open interfaces provide a great opportunity for be a server of choice. To understand what makes an open operating system, look at the components of the system. UNIX was conceived in the 1970s by employees of AT & T as an operating environment to provide services to software developers who were discouraged by the incompatibility of new equipment and lack of development tools for application development. The original intent of the UNIX architecture was to define a standard set of services to be provided by the UNIX kernel. These services are used by a shell that provides the command line interface. The functionality is enhanced through the provision of a library of programs. Applications constructed from the program library and custom code. The power and appeal of UNIX are in the common definition of core and shell and in the great amount of software that has been built and is available. Applications built on these standards can be ported to many different hardware platforms. The objectives of the original UNIX were very comprehensive and could have been reached except that the original operating system was developed under the auspices of AT & T. legal ramifications of the consent decree governing the decay of the regional Bell operating companies (RBOCs), AT & T unable to get into the computer business. As a result, the company had little motivation from the beginning to promote Unix as a product. To overcome this, and in an attempt to achieve an implementation of UNIX better suited to the needs of developers, the University of California at Berkeley and other institutions developed improved varieties of UNIX. As a result, the original purpose of a mobile platform has been compromised. The new products were undoubtedly better, but they were not compatible with each other or the original application. Until the mid-1980s, many versions of UNIX had increasing functionality were released. IBM, of course, enters the scene in 1986 with its own derivative of UNIX, AIX. Finally, in 1989, an agreement was reached on kernel based UNIX, shell functions and APIs. The computing community is close to a consensus on what the UNIX kernel and the shell will look like and the definition of the specific API. Figure 4.8 shows the components of the future standard UNIX operating system architecture.
During all these turns, a major UNIX problem has remained that differentiates it from DOS, Windows NT and OS / 2 on the client / server world. Because the hardware platforms on which resides UNIX come from many different manufacturers and are based on many different chipsets, the "off-the-shelf" software for PC that is sold is not yet available for UNIX. The software is sold and distributed in executable form, so it must be compiled and linked by the developer of the target platform. This means that organizations wishing to purchase UNIX software must be purchased for specific target platform you are using. This also means that when using many distributed platforms in a client / server, companies must buy different software versions for each platform.
UNIX is particularly desirable as a server platform for client / server computing because of the wide size range of platforms available and the huge base of software application and development available. Universities are helping to boost student UNIX UNIX graduates who only see during his student years. Government agencies insist on UNIX as a platform for all government projects. The combination of these pressures and technological change should ensure that compatibility will be mandatory for UNIX server platforms in the latter half of this decade. OSF initially Motif developed a GUI for UNIX, which has become the de facto standard UNIX GUI. The Distributed Computing Environment (DCE) are gaining acceptance as the standard for distributed application development, although its Distributed Management Environment has not yet achieved such broad support. OSF / 1, OSF UNIX kernel is defined, has only been adopted by DEC, although most other manufacturers have pledged to support it. OSF / 1 brings the promise of a core UNIX mic suitable for desktop environment than existing products. The desire for a UNIX standard encourages other organizations. For example, the IEEE addressed the UNIX unified theme by establishing a group to develop a portable operating system standard called POSIX. The aim is to develop a standard operating system ANSI. POSIX is not UNIX, but UNIX is. POSIX standards (which they undertake to comply with most vendors) currently exist. DEC's OpenVMS operating system For example, public support POSIX standards. POSIX at this point, however, does little to promote interoperability and portability because so little of the total standard has been finalized. Simple applications that will run through different POSIX compliant platforms, will be written. However, be limited by application developers not be able to use any of the features rich, not POSIX and functions that vendors offer beyond the basic core compatible with POSIX. X / Open began in Europe and has expanded to include most major U.S. computer manufacturers. X / Open is having a significant impact on the market because aims to establish a standard set of application programming interfaces (APIs) that enable interoperability. These interfaces are published in the X / Guide Portability Open. Applications running on operating systems that meet these interfaces communicate with each other and interoperate, even if the underlying operating system are different. This is the key objective of the client / server model. COSE announcement by HP, IBM, SCO, Sun and Univel (Novell / USL) in March 1993 at the Conference of uniforms is latest attempt to create common ground among UNIX operating systems. The initial announcement COSE desktop environment addresses only the user and the graphical user interface, although over time is expected to go further. COSE is a more pragmatic attempt to really "do." Another major difference from previous attempts to establish universal standards of UNIX is the participation of SCO and Sun. These two organizations have a substantial part of the UNIX market and have tended to promote the property approaches desktop interface. SCO provides open desktop environment, and Sun offers Open Look. Motif's commitment is an important concession from them and offers the first opportunity real interoperability and full transparency of suppliers to the platform user.
In October 1993, Novell decided to grant the rights to the UNIX name to X / Open so that all providers can develop and use standards UNIX UNIX name for their products. This symbolic gesture will eliminate some of the confusion in the market more than it really is the UNIX software. COSE is looking beyond the desktop for graphics, multimedia, object technology, and management systems. Network support includes Novell NetWare UNIX client network products, OSF DCE and SunSoft Open Network Computing. Novell is committed to presenting the NetWare UNIX Client X / Open for publication as a standard. In the graphics area, COSE plan participants to support a basic set of graphic services from the X Consortium, the developer X Windows. Addressing media, COSE participants intend to present two joint specifications in response to the request of the Interactive Multimedia Association technology. One of those specifications, called Distributed Media Services (DMS) defines an independent network infrastructure to support an integrated approach to the API and protocol data flow. The other-Desktop Integrated Media Environment-defines the media access and collaboration tools, including at least a basic tool for every data type supported by the DMS infrastructure. The resulting standard will provide users with continuous access to multimedia tools MultiFinder environments. COSE also deals with object technology, an area of guidance from IBM and Sun. The group will support the efforts of the Object Management Group (OMG) and its Policy Object Request Broker (CORBA) for the deployment and use of distributed objects. IBM already has a CORBA object system compatible with the beta version of AIX. Dom built an operating system called source code as a proof of concept in 1992. Sun has a big project, called distributed objects everywhere (DOE), which is producing results productivity very exciting. Finally, COSE will focus on the management of distributed file systems, distribution, and user groups, print queues, licenses for software installation and storage. It is no coincidence that these vendors come together to define a standard for UNIX at this time. The effort is COSE defensive reaction to the release of Windows NT at Microsoft. With this commitment to a team of 32-bit desktop and server operating system, Microsoft has had a lot of wind UNIX claims to technical superiority. Despite its many advantages as a desktop and server operating system, UNIX has never been widely accepted in the world general business favors DOS / Windows and Novell NetWare. A key problem at the enterprise level UNIX has been the lack of a single UNIX standard. UNIX has a well-established position as the operating system of choice for distributed relational databases from vendors such as Informix, Ingres, Oracle and Sybase. Most these vendors, however, the port their products to Windows NT as well. Any effort to reduce the problems associated with multiple variants of UNIX to do much to enhance the stature of UNIX as an option for Windows NT.
Back around this fantasy in your mind. All major hardware and software meet and agree to install a black box in their systems, in effect, remove the technological barriers. This black box will connect a variety of small operating systems, different hardware platforms, incompatible communication protocols, all applications and database systems, and even unlike security systems. And black box will do all this in a transparent manner, not only for end users but also for system administrators and application proposes the middle developers.2 OSF distributed computing environment (DCE) as the black box. DCE is the most important architecture defined for client / server model. Provides the bridge between existing investments in applications and new applications based on current technology. Figure 4.10 shows the architecture defined by the OSF. The first product components DCE were published in the third quarter of 1991. DCE competes directly with Sun's open network computing (ONC), the environment, and indirectly with many of the rules of the network. OSF / 1 and DCE is almost certain to win this battle because of the presence in the mass market of OSF sponsors. IBM has now committed to making your product AIX OSF / 1 compatible early 1994. It will be 1995 before the product is mature and complete enough to be widely used as part of business applications. In the meantime, suppliers and integrators to build systems using mobile devices and applications. The widespread availability of code developed in previous cases, the components of similar products will accelerate the process and allow development which builds on previous versions. DCE has been described as a layer in the OSI group model.3 DCE provides the communications link between pure in the lower layers and end-user applications.
These components are activated every time a local application requests data, services, processes or from somewhere. The OSF DCE says he'll do a network of multivendor systems appear as one independent team of developers applications, system administrators and end users. Thus, single system image is reached. Remote Procedure Call (RPC) and Presentation Services: Interface Definition Language (IDL) and RPC allow developers to transfer control and data over a network in a transparent way that helps to mask the complexity network. DCE RPC uses the originally developed by HP Apollo Network Computing System (NCS), with some improvements by DEC and IBM. NCS provides network data representation (NDR), a virtual data representation. NDR allows the exchange of data between various vendor products transparent. Conversions (if necessary) will be out without the intervention of the caller. Naming, security, file system, and data type conversions can occur when data is transported between different platforms. Appointment user-oriented names, specifying the computers, files, and people should be easily accessible in a distributed environment. These services directory should provide a common look and rules for all customers. DCE supports standard X.500 directory services, adding extensions December Domain Name Service (DECdns). The X.500 standard code is the service of Siemens Nixdorf X.500 DIR-X. Security: Distributed applications and services must identify users, access control to resources, and the protector of the integrity of all applications. DCE uses the Kerberos authentication service developed by MIT as part of its project Athena Network improved by Hewlett-Packard. This service is one of the main challenges for the development of products quickly, because nowadays very few products are developed with an awareness of this specification. Topics: This terminology is a method of supporting parallel execution through the management of multiple threads of control within a process that operates in a distributed environment. Themes allow the systems to implement various processes and forget about them until they are completed. This is especially important for network servers may have to handle many requests from many clients at the same time. They should be able to do this without having to wait for the previous application to complete. DCE is December concert using multithreaded architecture (CMA) of application. Service time: a time service synchronizes all the clocks of a distributed system for running applications may depend equivalent clock between processes. Note that many machines operating in many time zones can account for processes solution as part of a single application.
It is essential to agree on the time to manage scheduled events and events sequenced in time. DCE is using a modified December Distributed time synchronization service. Distributed File Services: By expanding the local file system across the network, users get full access to the configuration files remotely. DCE uses the Sun Network File System (NFS), version 2 and provides next generation capabilities the Andrew File System (AFS), developed at Carnegie-Mellon University and commercialized by Transact Corp. diskless operations under AFS are supported by work development made by Hewlett-Packard. PC Integration: Integration allows PCs with MS-DOS, Windows NT and OS / 2 to access file and print services outside MS-DOS environment. DCE uses the Microsoft LAN Manager / X Management: Although partly addressed by the above components, the management is so complex in a distributed environment, configuration heterogeneous OSF has defined a new architecture: distributed management environment (DME). DME provides a common framework for the management of autonomous and distributed systems. This framework provides consistent tools and techniques for managing different types of systems and allows providers to create applications management system work in a variety of platforms. OSF DME based on technology from Hewlett-Packard Open View of the product.
IBM SAA distributed environment. SAA was defined by IBM in 1986 as an architecture for integrating all of IBM computers and operating systems, including MVS, VM CMS /, OS/400, and OS/2-EE. SAA defines the standards for common user access (AUC) method, common programming interface (CPI), and a common communication link (APPC). To support the development of compatible applications AEA, AEA IBM describes frameworks (which are similar to API). The first part of SAA's AD / Cycle, the strategy for application development CASE AEA. AD / Cycle is designed to use third-party tools in the IBM mainframe hardware SAA and Repository Manager / MVS data storage facility. Several vendors have been selected by IBM as the AD / Cycle partners, namely: Intervolve, Knowledge Ware, Bachman, Synod, a systematic and stand Corp. Several products are already available, including the toolkit Easel Workbench, DB2 Bachman, CSP tools and the knowledge and tools UAB Ware MVS. Unfortunately, the most important component, Repository Manager, has not yet reached production quality MVS application and so far there are no plans for a client / server application. Many IBM customers involved original Manager in evaluating the UAB have returned the product in frustration. Recently, there has been much discussion about the need for quality production base object-oriented data management system in support of the entity-relationship (ER) is based repository. That's it, say some sources, is that the execution and performance practical. Another shortcoming of the strategy for SAA is the lack of support of open systems. Despite certain standards such as Motif, and LU6.2 application servers are identified as part of the AEA, the lack of support for AIX has prevented many organizations from adopting SAA. IBM has published all the rules of the Stabilisation and Association Agreement and has approved a number protocols such as LU6.2. The company has tried to open the SAA software development world. IBM's director of open systems strategy, George Siegel, IBM said it believes in the opening through interfaces. Thus, the full definition of API allows other manufacturers to develop products that interact with IBM products and the others. Recent announcements, such as support for CICS AIX, suggest a gradual movement to include AEA AIX platforms. The first application of AEA that IBM launched the Office Vision, was a disaster. The product is constantly missed shipping dates and lacked many of the features promised. IBM has largely abandoned the product now and is working in close collaboration with Lotus and its computing initiatives working group. IBM has always defined the common database, user interface, and communications standards across all platforms. This certainly provides the opportunity to build customer AEA supports server applications.
IBM has clarified its System View product DME. View System defines APIs to enable interoperability between products from different manufacturers. Expected to be the vehicle for linking mainframe AIX centralized sites. IBM stated that it is an open system View structure for the integration of OSI, SNA and TCP / IP. At this time, System View is a set of guidelines to help developers third party software and customers to integrate systems and storage management applications, data definitions and access methods. The guidelines are intended to further support the concepts of a single system image.
In view of this, it is significant that the recent introduction of CICS for OS / 2, AIX and OS/400 and the announcement of support for AIX means that a single transaction processing platform defines the range of products. Applications developed under OS / 2 can be ported to interoperate between OS / 2, OS/400, MVS, and finally, AIX, without modification. COBOL and C are common programming languages for each platform. Application Server is the language of common access data on all platforms. The failure of the SAA is due to the complexity of heterogeneous product lines of IBM and the desire of many organizations away from ownership of open systems solutions. This recognition drove IBM to announce its new business plan open to replace the old system Application Architecture (AEA) to plan a strategy for open network. System View is a product key network connecting IBM OS / 2, Unix and AS/400 operating systems. Traditional Network Systems Architecture (SNA) networks will be replaced by new technologies such as Advanced Peer-to-Peer Communications (APPC) and Advanced Peer-to-Peer Networking.
Written by: Kh. Atiar Rahman
Against the Official
Financial Management Reform Program
About the Author
written by: Kh. Atiar Rahman
Counter Part Officer
Financial Management Reform Programme
Ministry of Finance, Finance Division
