File Management Systems Overview

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Questions and Answers

What is a key advantage of direct record organization?

Records are updated more quickly than in sequential files. (correct)

Adding and deleting records is typically slower.

It allows for preservation of record order.

It provides complete random access without any restrictions.

Which of the following is a disadvantage of using direct record organization?

Deleting records is a complex process.

All records are stored in perfect sequential order.

Records can only be accessed sequentially.

There is a risk of hashing algorithm collisions. (correct)

How does the access method in direct record organization work if starting from the first record?

Access is sequential by relative addressing. (correct)

Access is always random and unrestricted.

Only the first record can be accessed directly.

Access is limited to the last record added.

What challenge may arise from using a hashing algorithm in direct record organization?

It can lead to records being assigned the same logical address. (A) Signup and view all the answers

What is one way that direct record organization differs from sequential files?

Direct record organization allows for quicker updates. (B) Signup and view all the answers

What plays a crucial role in the efficiency of a File Manager?

The system's file organization (D) Signup and view all the answers

Which file storage technique allows for flexible space allocation for records?

Variable-length record storage (C) Signup and view all the answers

Which statement accurately describes direct file access?

It allows for immediate retrieval of any record. (C) Signup and view all the answers

Why is data compression important in file storage?

It reduces the data transfer time over networks. (A) Signup and view all the answers

What is a characteristic of sequential access file storage?

It processes records in the order they were stored. (C) Signup and view all the answers

How do file naming conventions typically function?

They often indicate the file type via extensions. (C) Signup and view all the answers

What is one of the key components of user access protection for files?

Encryption methods (C) Signup and view all the answers

What distinguishes fixed-length record storage from variable-length record storage?

Fixed-length records have a predetermined size. (C) Signup and view all the answers

What is one of the primary responsibilities of a file management system?

Creating, deleting, modifying, and controlling access to files (C) Signup and view all the answers

Which of the following is NOT a task performed by a file manager?

User authentication (B) Signup and view all the answers

How does a file manager efficiently manage available storage space?

By implementing policies on file storage (C) Signup and view all the answers

What does file deallocation involve?

Restoring files to storage and communicating availability (D) Signup and view all the answers

Why is tracking file storage important for a file manager?

To know where each file is stored and ensure efficient access (D) Signup and view all the answers

What is involved in the policy implementation responsibility of the file manager?

Determining how files are stored and accessed (B) Signup and view all the answers

Which statement reflects a file manager's role in providing access to files?

Facilitating controlled access based on user permissions (B) Signup and view all the answers

What is a key benefit of efficient file allocation?

Minimizing the resources used while managing file access (A) Signup and view all the answers

What is the primary purpose of a file extension in file naming conventions?

To identify file type or contents (D) Signup and view all the answers

In Windows file naming conventions, how is the complete file structure represented?

Drive label, directory name, relative name, and extension (A) Signup and view all the answers

Which of the following best describes fixed-length records?

Allows for easy direct access to data (B) Signup and view all the answers

What happens if a fixed-length record size is too small for the data it is meant to store?

The data is truncated, leading to potential corruption (A) Signup and view all the answers

What is a typical requirement when an extension is unknown?

The user must specify the file type manually (B) Signup and view all the answers

What is the primary function of a field in a data structure?

To store related bytes identified by user specifications (C) Signup and view all the answers

When comparing Windows and UNIX/Linux file paths, which characteristic is unique to UNIX/Linux?

Uses forward slashes for directories (C) Signup and view all the answers

How is a record defined in the context of data organization?

A combination of multiple fields serving a specific purpose (D) Signup and view all the answers

What is a potential consequence of using fixed-length records that are larger than the actual data stored?

Storage space is wasted (A) Signup and view all the answers

What characterizes a flat file in data management?

It contains no connections to other files and lacks dimensionality (C) Signup and view all the answers

How many characters typically make up a file extension?

Two to four characters (B) Signup and view all the answers

Which option best describes a file in relation to application programs?

Information that is utilized by specific application programs (C) Signup and view all the answers

What is the role of folders in data organization?

To contain listings of filenames and their attributes (D) Signup and view all the answers

How do interconnected files enhance data accessibility?

By allowing users to easily navigate and retrieve stored data (A) Signup and view all the answers

Which statement accurately reflects the purpose of a database program?

To manage groups of related files and enhance data retrieval (D) Signup and view all the answers

What is a director in the context of data files?

A system that contains instructions and data (B) Signup and view all the answers

What is a key characteristic of indexed storage?

Every file has its own index block. (C) Signup and view all the answers

Which statement is true regarding sequential file organization?

It can only access records in sequence. (B) Signup and view all the answers

How does indexed storage affect large files?

It can result in several index levels that complicate access. (B) Signup and view all the answers

What is the most flexible method of file organization?

Indexed sequential files. (B) Signup and view all the answers

Which of the following statements is false regarding record access in indexed storage?

Indexed storage provides improvements in storage space usage. (B) Signup and view all the answers

How does the current byte address (CBA) function in sequential file access?

It is updated every time a record is accessed. (B) Signup and view all the answers

What is the relationship between indexed storage and the organization of file records?

Indexed storage uses an index block to link records for efficient access. (C) Signup and view all the answers

Which file organization method is considered the least flexible?

Sequential files. (A) Signup and view all the answers

Study Notes

File Management - Chapter 8

This chapter describes how files are managed, file naming conventions, storage types, and access control techniques.

Learning Objectives (1 of 2)

After completing this chapter, students will be able to describe how files are managed.
Students will describe how files are named and the role of extensions.
Students will be able to discuss how variable-length record storage differs from fixed-length records.
Students will be able to compare different file storage techniques.

Learning Objectives (2 of 2)

Comparisons of sequential and direct file access
Access control techniques and how they compare
Importance of data compression in file storage

Introduction

File Manager's efficiency depends on:
- How the system organizes files
- How files are stored
- Structure of each file's records
- Protection of users' access to files

The File Manager

Also known as the file management system software.
Responsible for controlling access to files and managing resources used by files.

Responsibilities of the File Manager (1 of 3)

File storage tracking (keeping track of where each file is stored.)
Policy implementation (determining where and how files are stored)
Efficient use of available storage space
Providing efficient file access
File allocation (if user access is cleared)
Record file use
File deallocation
Returning file to storage
Communicating file availability

Responsibilities of the File Manager (2 of 3)

Policy determines:
- File storage location
- How a system and user can access a file
Access to material has two factors:
- Access to material
- Flexibility of access

Responsibilities of the File Manager (3 of 3)

Preventing system malfunctions (security checks, account numbers, and passwords)
File allocation (activating secondary storage, loading files, and updating records)
File deallocation (updating file tables, rewriting files, and notifying waiting processes)
File management in the cloud

Definitions (1 of 3)

Field: A group of related bytes, identified by the user (name, type, size)
Record: A group of related fields, grouping related records used by specific applications
File: A group of related records, a collection of information utilized by application programs. It is a flat file, with no connections to other files; it's not dimensioned.

Definitions (2 of 3)

Database: A group of related files
Program Files: Contain instructions
Data Files: Contain data
Directories (folders): Listings of filenames and attributes

Definitions (3 of 3)

Files consist of records.
Records are made up of fields. (Figure 8.1)

Interacting with the File Manager (1 of 3)

Common user commands: OPEN, DELETE, RENAME, COPY

Interacting with the File Manager (2 of 3)

Device-independent if information about physical location, medium, and network knowledge is available in the device driver.
Physical location knowledge not needed (cylinder, surface, sector)
Device medium knowledge not needed (tape, magnetic disk, optical disk, flash storage)
Network knowledge not needed

Interacting with the File Manager (3 of 3)

Logical commands when accessing a file:
- Broken into lower-level signals (example: READ)
- Moving read/write heads to record cylinder
- Waiting for rotational delay (sector passes under read/write head)
- Activating appropriate read/write head and reading record
- Transferring record to main memory
- Sending flag, indicating free device for another request
- Monitoring for error conditions

Typical Volume Configuration (1 of 4)

Volume: Each secondary storage unit (removable or non-removable)
Structure: Multi-file volume (contains many files)
Structure: Multi-volume files (extremely large files spread across several volumes)
Each volume in the system is given a name by the file manager. Name and descriptive information are written on the storage device (innermost part of CD, beginning of tape, first sector of outermost tracks.)

Typical Volume Configuration (2 of 4)

(Figure 8.3)
Volume descriptor (stored at the beginning of each volume) includes vital storage unit information.

Typical Volume Configuration (3 of 4)

Master file directory (MFD)
- Stored immediately after volume descriptor.
Lists:
- File names and characteristics
- File names (program, data, system files)
- Subdirectories listed in MFD
- Supported by file manager

Typical Volume Configuration (4 of 4)

Single directory per volume
- Supported by early operating systems
Disadvantages:
- Long search time for individual files
- Directory space can fill before disk storage space
- Users cannot create subdirectories
- Users cannot safeguard files

File-Naming Conventions (1 of 4)

Filename components: Relative filename and extension
Complete filename (absolute filename) Includes all path information
Relative filename: Name without path information; appears in directory listings, folders; differentiates filenames within a directory; varies in length; operating system-specific

File-Naming Conventions (2 of 4)

Table 8.1: Typical file name parameters for operating systems (listed alphabetically)

File-Naming Conventions (3 of 4)

Extensions: Appended to relative filename; two to four characters; separated from relative filename by period; identifies file type or contents (example: BASIA_TUNE.MPG); unknown extensions requires user intervention

File-Naming Conventions (4 of 4)

Operating system specifics: Windows (drive label, directory name, relative name, extension) and UNIX/Linux (forward slash, master directory/root, subdirectories, file's relative name)

File Organization

Arrangement of records within files
All files composed of records
Modify command: Request to access a record within a file

Record Format (1 of 2)

Fixed-length records: Direct access is easy, but if record is smaller than needed, data is truncated.
Variable-length records: Direct access is difficult as empty spaces and character truncations are not allowed.

Record Format (2 of 2)

Data stored in fixed-length fields (truncated if exceeds field limit) (Figure 8.6)
Data stored in variable-length fields (not truncated) (Figure 8.6)

Physical File Organization (1 of 6)

Physical organization of a file is determined by
- Record arrangement
- Medium characteristics
- Magnetic disk file organization (Sequential, Direct, Indexed Sequential)
- File organization scheme selection considerations:
  - Data volatility (frequency of additions and deletions)
  - File activity (percentage of accessed records)
  - File size
  - Response time (time user waits for completion)

Physical File Organization (2 of 6)

Sequential record organization: Records are stored and retrieved serially (one after the other).
- Easy to implement
- Search begins at the beginning of the file until the record is found

Physical File Organization (3 of 6)

Direct record organization: Uses direct access files, requiring direct access storage device implementation and random organization.
Relative address record identification: Known as logical addresses, computed when records are stored and retrieved using hashing algorithms that transform each key into a number.

Physical File Organization (4 of 6)

Direct record organization - Advantages: Fast record access, sequential access is easy when starting at first relative address and incrementing to next record, updates are faster than sequential files (no preservation of records order).
Direct record organization - Disadvantages: Adding/deleting records is quick, hashing algorithm collisions: records with unique keys may generate the same logical address.

Physical File Organization (5 of 6)

Hashing algorithm causes collision (Figure 8.7)
- Uses combination of street address and postal code
- Hashes algorithm generates same logical address (152132737) for 3 different records.

Physical File Organization (6 of 6)

Indexed sequential record organization: Best of sequential and direct access; indexed sequential access method (ISAM) software; advantage—no collisions.
Divides ordered, sequential files into equal-sized blocks to contain the highest record key and physical data block location.
Search index file, overflow areas

Physical Storage Allocation (1 of 2)

File manager works with files as whole units or logical units or records, each file has records subdivided into fields. Application programs (used by the file manager) manage record structure. File storage refers to record storage. Records within a file must have the same format, and record lengths may vary.

Physical Storage Allocation (2 of 2)

Figure 8.8. Different record formats; fixed-length records occupy pre-determined locations versus variable length records which can vary.

Contiguous Storage

Records stored one after the other
Advantages:
- Any record found once starting address is known, easy access
Disadvantages:
- Difficult file expansion, and fragmentation.

Noncontiguous Storage (1 of 5)

Files use available storage space
File records stored in contiguous manner (if enough space)
Remaining file records placed into sections (extents)
Extents linked together with pointers

Noncontiguous Storage (2 of 5)

File extents linked by storage level
Directory entry includes filename, storage location of first extent, location of last extent, and total number of extents (not counting first)
Directory level
- Each extent listed with physical address, size, pointer to next extent
- Null pointer indicates last extent

Noncontiguous Storage (3 of 5)

Advantages: Eliminates external storage fragmentation, eliminates need for compaction
Disadvantages: No direct access support, cannot determine specific record's location.

Noncontiguous Storage (4 of 5)

Noncontiguous file storage linking in storage level
- Directory lists starting and ending addresses, number of extents in use (Figure 8.10)

Noncontiguous Storage (5 of 5)

Noncontiguous storage allocation with linking at directory level. For each of the files in Figure 8.10, the directory lists the file's starting address, ending address, and the number of extents used (Figure 8.11)

Indexed Storage (1 of 2)

Allows direct record access.
Index block, bringing pointers together in linking every extent file. Every file has a separate index block, disk sector addresses for the file, entries ordered in sectors linked, and support for sequential and direct access.

Indexed Storage (2 of 2)

Indexed storage allocation with a one-level index, allowing direct access from the index block to each record shown in figures 8.10 and 8.11 (Figure 8.12)

Access Methods

Access methods dictated by file organization (indexed sequential files most flexible, sequential files least flexible)
Sequential file organization supports only sequential access; records are fixed or variable length, accesses next sequential record.
Current address of last byte is read and updated every time a record is accessed.

Sequential Access (1 of 2)

Update CBA
Fixed-length records
- Increment CB
- CBA = CBA + RL
Variable-length records
- Add length of record (RL), plus the numbers of bytes used to hold the CBA record to CBA, giving CBA= CBA + N + RL

Sequential Access (2 of 2)

Fixed vs variable-length records: Fixed-length have same number of bytes (record length is constant), versus variable length using a variable record length (RL) (Figure 8.13)

Direct Access

Mixed-length records (desired record number) where CBA = (RN — 1) * RL
Variable-length records
- Virtually impossible to get address of the desired record
- Requires sequential record search
Indexed sequential file
- Sequentially or directly accessed
- Index file searched for pointers to data blocks

Levels in a File Management System (1 of 3)

File manager, Basic File System, Device, Device Manager
Modules: access control module, device interface module, physical file system, logical file system (Figure 8.14) shows the communications flow

Levels in a File Management System (2 of 3)

Level implementation is structured and modular, programming techniques are hierarchical
Top module passes info to lower module; modules further subdivided for more specific tasks, using information in the basic file system, transforming record numbers to byte addresses

Levels in a File Management System (3 of 3)

Verification at every level
Directory level: File system checks if the requested file exists, and access control module ensures that access to the file is allowed
Logical file system: Checks if requested byte address is within file limits
Device Interface Module: Checks for the existence of the storage device

Access Control Verification Module

File sharing: Data files, user-owned program files, system files
Advantages: Saving space, synchronized updates, enhanced resource efficiency
Disadvantages: Need to protect file integrity
File actions: READ only, WRITE only, EXECUTE only, DELETE only, or a combination

Access Control Matrix (1 of 2)

Advantages: Easy to implement; works well with few files, few users
Table 8.3: An access control matrix showing access rights for each user for each file

Access Control Matrix (2 of 2)

Disadvantages: As files/users increase, matrix increases to potentially beyond main memory capacity, wasting space due to null entries
Table 8.4: The five access codes for User 2; assigns 1 for each checkmark and zero for blank spaces.

Access Control Lists (1 of 2)

Modification of Access Control Matrix technique
Table 8.5: Access control list (ACL) showing which users are allowed to access each file. Uses storage space more efficiently than a matrix

Access Control Lists (2 of 2)

Contains user names
User access grouped under
- SYSTEM (administrator)
- OWNER (user)
- GROUP
- All users belonging to group have access
- WORLD (All other users in system)

Capability Lists

Lists every user and respective file access
Controls user access to devices
Table 8.6 is a capability list, showing files for each user using less storage space than an access control matrix

Data Compression

Lossless: Retains all data within a file (used with text and arithmetic applications)
Lossy: Removes some data without altering file quality (used with image and sound files)

Text Compression

Records with repeated characters are compressed by replacing repeated characters with a code.
Repeated terms compressed using symbols to represent commonly used words.
Example—University student database, common words, front-end compression

Image and Sound Compression

Lossy compression: Cannot reconstruct the original file, highly dependent on file type.
- JPEG (still images)
- MPEG (video images)
International Organization for Standardization (ISO): World's leading developer of international standards.

Conclusions

File manager controls every file, process, and user commands.
Manages access control procedures, maintaining file integrity and security.
File organization: sequential, direct, indexed sequential
Physical storage: contiguous, noncontiguous, indexed
Record types: fixed-length versus variable-length
Access control methods
Data compression techniques

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Description

This quiz explores key concepts and advantages of direct record organization in file management systems. You'll answer questions about access methods, storage techniques, and the importance of data compression. Test your understanding of the fundamental differences between direct and sequential access methods.