The table model consists of a single, two-dimensional array of data elements, where all members of a given column are assumed to be similar values, and all members of a row are assumed to be related to one another. For instance, columns for name and password that might be used as a part of a system security database. Each row would have the specific password associated with an individual user. Columns of the table often have a type associated with them, defining them as character data, date or time information, integers, or floating point numbers.

Techniques of File Organization

The three techniques of file organization are:

1. Heap (unordered)
2. Sorted
   1. Sequential (SAM)
   2. Line Sequential (LSAM)
   3. Indexed Sequential (ISAM)
3. Hashed or Direct

In addition to the three techniques, there are four methods of organizing files. They are sequential, line-sequential, indexed-sequential, inverted list and direct or hashed access organization.

File organization determines the set of access methods for Storing and retrieving records from a file so file organization means access methods for accessing and retriving files from storage.

In file organization we must consider a better way for storaging our file to improve query performance for getting data fromstorage medium.

This is the most common structure for large files that are typically processed in their entirety, and it's at the heart of the more complex schemes.

In indexed file organization, the records of the file are stored one after another in the order they are added to the file.

In contrast to RELATIVE files, records of a INDEXED SEQUENTIAL file can be accessed by specifying an ALPHANUMERIC key in the READ statement (the KEY) .

Responsibility of File Management.

1. Mapping of logical file address to physical disk address
2. Management of disk space & allocation - deallocation.
3. Keeping track of all files in system
4. Support for protection & sharing of files.
 

Disk Scheduling

1. First come first served (FCFS)

2. Shortest Seek Time First

3. Scan Scheduling also called Elevator Algorithm