Limitations of the File-Based Approach

 


Limitations of the File-Based Approach


This brief description of traditional file-based systems should be sufficient to discuss the limitations of this approach .


 1 . Separation and isolation of data

When data is isolated in separate files, it is more difficult to access data that should be available.

With file systems, such processing is difficult. The application developer must synchronize the processing of two files to ensure the correct data is extracted. This difficulty is compounded if we require data from more than two files.


2 . Duplication of data

Owing to the decentralized approach taken by each department, the file-based approach encouraged, if not necessitated, the uncontrolled duplication of data .

Uncontrolled duplication of data is undesirable for several reasons, including:

  • Duplication is wasteful. It costs time and money to enter the data more than once. 
  • It takes up additional storage space, again with associated costs. Often, the duplication of data can be avoided by sharing data files. 
  • Perhaps more importantly, duplication can lead to loss of data integrity; in other words, the data is no longer consistent. 


3. .Data dependence 

As we have already mentioned, the physical structure and storage of the data files and records are defined in the application code. This means that changes to an existing structure are difficult to make.

For example, increasing the size of the PropertyForRent address field from 40 to 41 characters sounds like a simple change, but it requires the creation of a one-off program (that is, a program that is run only once and can then be discarded) that converts the PropertyForRent file to the new format. 

This program has to: 

  • Open the original PropertyForRent file for reading; 
  • Open a temporary file with the new structure; 
  • Read a record from the original file, convert the data to conform to the new structure, and write it to the temporary file. 
  • Repeat this step for all records in the original file; 
  • Delete the original PropertyForRent file; 
  • Rename the temporary file as PropertyForRent.

Clearly, this could be very time-consuming and subject to error. This characteristic of file-based systems is known as program–data dependence. 


4 . Incompatible file formats

Because the structure of files is embedded in the application programs, the structures are dependent on the application programming language. 

For example, the structure of a file generated by a COBOL program may be different from the structure of a file generated by a ‘C’ program. 

The direct incompatibility of such files makes them difficult to process jointly.

5 . Fixed queries/proliferation of application programs

  • There was no provision for security or integrity.
  • Recovery, in the event of a hardware or software failure, was limited or non-existent.
  • Access to the files was restricted to one user at a time – there was no provision for shared access by staff in the same department.


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