----------------------------------------------------------- New Message on MumbaiUserGroup
----------------------------------------------------------- From: srivatsahg Message 2 in Discussion Thnx Bala that was very informative >From: "explorebala" <[EMAIL PROTECTED]> >Reply-To: "MumbaiUserGroup" <[email protected]> >To: [email protected], [email protected], >[email protected] >Subject: DBMS-overview >Date: Tue, 5 Sep 2006 01:49:39 -0700 > > > > > > > > > > > > > > New Message on MumbaiUserGroup > > > > > > > > DBMS-overview > > > > > Reply > > > > ? > > Reply to Sender > ??Recommend > > Message 1 in Discussion > > > > > > > > From: > explorebala > > > > > hi folkz! today onwards we will discuss abt DBMS > >1. Introduction > >DBMS A Database is a collection of interrelated data and a Database >Management System is a set of programs to use and/or modify this data. >1. 1 Approaches to Data Management >File-Based Systems >Conventionally, before the Database systems evolved, data in software >systems was stored in and represented using flat files. >Database Systems >Database Systems evolved in the late 1960s to address common issues in >applications handling large volumes of data which are also data intensive. >Some of these issues could be traced back to the following disadvantages of >File-based systems. >Drawbacks of File-Based Systems > >As shown in the figure, in a file-based system, different programs in the >same application may be interacting with different private data files. >There >is no system enforcing any standardized control on the organization and >structure of these data files. >Data Redundancy and Inconsistency >Since data resides in different private data files, there are chances of >redundancy and resulting inconsistency. For example, in the above example >shown, the same customer can have a savings account as well as a mortgage >loan. Here the customer details may be duplicated since the programs for >the >two functions store their corresponding data in two different data files. >This gives rise to redundancy in the customer's data. Since the same data >is >stored in two files, inconsistency arises if a change made in the data in >one file is not reflected in the other. >Unanticipated Queries >In a file-based system, handling sudden/ad-hoc queries can be difficult, >since it requires changes in the existing programs. >Data Isolation >Though data used by different programs in the application may be related, >they reside in isolated data files. >Concurrent Access Anomalies >In large multi-user systems the same file or record may need to be accessed >by multiple users simultaneously. Handling this in a file-based systems is >difficult. >Security Problems >In data-intensive applications, security of data is a major concern. Users >should be given access only to required data and not the whole database. In >a file-based system, this can be handled only by additional programming in >each application. >Integrity Problems >In any application, there will be certain data integrity rules which needs >to be maintained. These could be in the form of certain >conditions/constraints on the elements of the data records. In the savings >bank application, one such integrity rule could be Customer ID, which is >the unique identifier for a customer record, should be non-empty. There can >be several such integrity rules. In a file-based system, all these rules >need to be explicitly programmed in the application program. >It may be noted that, we are not trying to say that handling the above >issues like concurrent access, security, integrity problems, etc., is not >possible in a file-based system. The real issue was that, though all these >are common issues of concern to any data-intensive application, each >application had to handle all these problems on its own. The application >programmer needs to bother not only about implementing the application >business rules but also about handling these common issues. > >regards >bala nagarajan > >_________________________________________________________________ >Live the life in style with MSN Lifestyle. Check out! >http://content.msn.co.in/Lifestyle/Default > > > > > > > > > View other groups in this category. > > > > > > > > > > > > > >Also on MSN: >Start Chatting?|?Listen to Music?|?House & Home?|?Try Online Dating?|?Daily >Horoscopes > > > > > > > > > > > To stop getting this e-mail, or change how often it >arrives, go to your E-mail Settings. > > > Need help? If you've forgotten your password, > please go >to Passport Member Services. > > For other questions or feedback, go to our > Contact Us >page. > > > If you do not want to receive future e-mail > from this >MSN group, or if you received this message by mistake, please click the >"Remove" link below. On the pre-addressed e-mail message that opens, simply >click "Send". Your e-mail address will be deleted from this group's mailing >list. > > > Remove my e-mail address from MumbaiUserGroup. > > > > > > > _________________________________________________________________ Live the life in style with MSN Lifestyle. 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