Criteria of choice SUBD at creation of information systems

The choice of a control system of databases (SUBD) represents complex

Multipleparameter problem  also is one of the important stages by development

Applications of databases. The chosen software product should satisfy as

Current, and to the future needs{requirements} of the enterprise, thus it is necessary to take into account

Financial expenses for purchase of the necessary equipment, system,

Development of the necessary software on its{her} basis, and also training

The personnel. Besides it is necessary to be convinced, that new SUBD it is capable to bring

To the enterprise real benefits.

In given clause{article} by results of the analysis of accessible sources, for example [1-5],

Attempt to formulate the requirement or, otherwise, criteria is done{made} at

Choice SUBD, classification of requirements / criteria is resulted. Obviously, most

The simple approach at choice SUBD is based on a rating of in what measure existing

Systems meet the basic requirements of the created project information

Systems. More complex  and expensive variant is creation

The test project on the basis of several SUBD and the subsequent choice most

Suitable from candidates. But also in this case it is necessary to limit a circle

Possible{Probable} systems, leaning{basing} on certain criteria of selection. Generally speaking, the list

Requirements to SUBD, used at the analysis of this or that information system,

Can change depending on objects in view. Nevertheless it is possible

To allocate some groups of criteria:

* Modelling the data

* Features of architecture and functionalities

* The control of job of system

* Features of development of applications

* Productivity

* Reliability

* Requirements to a working environment

* The mixed criteria

Let's consider each of these groups separately.

Modelling of the data.

* Used model of the data. There is a set of models of the data;

The most widespread - hierarchical, network, relational,

Objective - relational and objective. A question on use of this or that model

Should be solved at the initial stage of designing of information system.

* Triggers and stored{kept} procedures. The trigger - the program of a database,

Caused every time at an insert, change or removal{distance} of a line of the table.

Triggers provide check of any changes on a correctness, before these

Changes will be accepted. Stored{kept} procedure - the program which is stored{kept} on

The server also it can be caused by the client. As stored{kept} procedures are carried out

Directly on the server of a database, higher is provided

Speed, rather than at performance of the same operations by means of the client of a DB. In

Various software products for realization of triggers and stored{kept} procedures

Various tools are used.

* Search engines. Some modern systems have built - in

Additional means of contextual search.

* The stipulated types of the data. Here it is necessary to take into account two actually

Independent criterion: the base or basic types of the data incorporated in system,

And presence of an opportunity of expansion of types. While deviations{rejections} base

Sets of types of the data at modern systems from certain standard, usually,

Are insignificant, mechanisms of expansion of types of the data in systems of this or that

The manufacturer essentially differ.

* Realization of language of searches. All modern systems are compatible with

Standard language of a data access sql-92, however many of them realize those

Or other expansions of the given standard.

Features of architecture and functionalities.

* Mobility. Mobility is an independence of system of Wednesday, in

As which she works. Environment{Wednesday} in this case is as the equipment, and

The software (operational system).

* Scalability. At choice SUBD it is necessary to take into account, whether can

The given system to correspond{meet} to growth of information system, and growth can

To be shown in increase in number of users, volume of the stored{kept} data and volume

The processable information.

* Distribution. A principal cause of application information

Systems on the basis of databases the aspiration to unit sights at all is

The information of the organization. The most simple and reliable approach - centralization

Storages and data processing on one server. Unfortunately, it not always

Probably also it is necessary to apply the distributed{allocated} databases. Various systems

Have different opportunities of management of the distributed{allocated} databases.

* Network opportunities. Many systems allow to use wide

Range of network reports and services for job and administrations.

The control of job of system

* The control of use of memory of a computer. The system can have

Opportunity of management of use both operative memory, and disk

Spaces. In the second case it can be expressed, for example, in compression of bases

The data, or removal{distance} of superfluous files.

* Autotune. Many modern systems include

Opportunities samokonfigurirovanija which, as a rule, lean{base} on

Results of job of services of self-diagnostics of productivity. Given

The opportunity allows to reveal weak places of a configuration of system and

Automatically to adjust her  to the maximal productivity.

Features of development of applications.

* Many manufacturers SUBD issue also means of development of applications

For the systems. As a rule, these means allow in the best way

To realize all opportunities of the server, therefore at analysis SUBD costs{stands}

To consider as well opportunities of means of development of applications.

* Means of designing. Some systems have means

Automatic designing, both databases, and applied programs.

Means of designing of various manufacturers can essentially

To differ.

* Multilanguage support. Support of a plenty national

Languages expands a scope of system and the applications constructed on her

To basis.

* Opportunities of development of web-applications. At razrabotkerazlichnykh

Applications frequently there is a necessity to use an opportunity of environment{Wednesday}

internet. Means of development of some manufacturers have the big set

Tools for construction of applications under web.

* Supported programming languages. A wide spectrum used

Programming languages raises availability of system to developers, and

Also can it essential affect speed and functionality

Created applications.

Productivity.

* A rating tpc (transactions per cent). For testing

Productivity various means are applied, and there is a set

Test ratings. One of the most popular and objective is

The tpc-analysis of productivity of systems. Actually tpc the analysis considers{examines}

Composition SUBD and equipments on which this SUBD works. A parameter tpc-

This attitude{relation} of quantity{amount} of searches processable for a certain time interval to

Cost of all system.

* Opportunities of parallel architecture. For maintenance parallel

Data processing exists, at least, two approaches: rasparallelivanie

Processings of sequence of searches about some processors, or

Use of the several computers - clients working from one DB, which

Unite in the so-called parallel server.

* Opportunities optimizirovanija searches. At use

Not procedural languages of searches their performance can be not optimum. Therefore

It is necessary to make process of optimization of searches, i.e. to choose such way

Performance, when on initial performance of search by his  syntactic

And semantic transformations the procedural plan of performance is developed

Search, the optimal at managers existing in a database

Structures.

Reliability.

The concept of reliability of system has many senses is and safety of the information

Independent of any failures, and non-failure operation of job of system in any conditions, and

Maintenance of protection of the data from the non-authorized access.

* Restoration after failures. At occurrence program or

Hardware failures integrity, and serviceability of all system can be

It is broken. How the mechanism of restoration is effectively planned after

Failures, viability of system depends.

* Reserve copying. As a result of hardware failure can be

The data carrier and then is in part damaged{injured} or put out of action

Restoration of the data is impossible, if not has been stipulated reserve

Copying of a database, or its{her} part. Reserve copying rescues and in

Situations when there is a logic failure of system, for example at erroneous

Removal{Distance} of tables. There is a set of mechanisms of reservation of the data

(storage of one or more copies of all database, storage of a copy of its{her} part,

Copying of logic structure, etc.). Frequently in system it is pawned

Opportunity of use of several such mechanisms.

* Recoil of changes. At performance of transaction it is applied idle time

The rule - or transaction is carried out completely, or not carried out in general.

It means, that in case of failures, all results not finished

Transactions should be cancelled. The mechanism of recoil can have various

Speed and efficiency.

* Multilevel system of protection. Information system of the organization

Almost always includes the classified information, therefore for prevention

The non-authorized access the service of identification of users is used.

The level of protection can be various. Except for direct identification

Users at an input{entrance} in system the mechanism can be used also

Encryptions of the data by transfer on communication lines

Requirements to a working environment.

* Supported hardware platforms.

* Minimal requirements to the equipment.

* The maximal size of addressed memory. As almost all

Modern systems use the file system, the important factor

Is what maximal volume of physical memory they can

To use.

* Operational systems under the control of which it is capable to work

SUBD.

The mixed criteria.

* Quality and completeness of the documentation. Unfortunately, not all systems have

The full and detailed documentation.

* Lokalizovannost`. An opportunity of use of national languages not

In all systems it is realized completely.

* Model of formation of cost. As a rule, manufacturers SUBD

Use the certain models of formation of cost. For example, cost

The same product can change essentially depending on that,

How much users with it  will work.

* Stability of the manufacturer.

* Prevalence SUBD.

Even if simply to mark as far as are good or plokhi the selected parameters in

Case of everyone concrete SUBD comparison already two various systems is

Labour-consuming problem . Nevertheless, the precise and deep comparative analysis on

The basis of the set forth above criteria in any case will help to choose rationally

Suitable system for the concrete project, and the spent efforts will not be

Vain. The list of criteria will help to realize scale of a problem  and to execute

Its{Her} adequate production.

It is necessary to note, that on existing practice the decision on use of that

Or other SUBD is accepted by one person - usually, the director, and he

Can lean{base} at all on technical criteria. Here the role can play

Such, from the technical point of view, insignificant factors as advertising

Promotion of company - manufacturer SUBD, use of concrete systems on others

The enterprises, cost. Thus last factor can be treated in two

Opposite senses depending on a financial status and politics

The enterprises. On the one hand, it can be a principle, - the more dearly{expensively}, the better. On the other hand - kul`tivirovanie almost free-of-charge use of a product,

Down to "breaking" his  license protection. Obviously, last approach is fraught

Collisions also cannot lead to to success in long-term job.