OS File Management And I/O Management Quiz

Records are treated as a unit means that a group of related data elements are treated together as a single entity. This implies that when performing operations or making changes to the data, all the data elements within a record are considered together. This approach ensures data integrity and consistency within the database. Therefore, the statement "Records are treated as a unit" is true, as it emphasizes the concept of treating records as a cohesive unit rather than individual data elements.

Indexed Sequential is the correct answer because it combines the benefits of both sequential and indexed file organization. In an indexed sequential file, the records are stored in a sequential order, allowing for efficient sequential access. However, it also includes an index that allows for direct access to specific records, reducing the time required to access a single record. This makes it a more efficient option compared to a purely sequential file organization.

RAID 1 does not use parity for data protection. In RAID 1, also known as mirroring, data is duplicated across multiple drives. Each drive in the RAID 1 array contains an identical copy of the data, providing redundancy and protection against drive failures. Parity, on the other hand, is used in RAID 4, RAID 5, and RAID 6 to provide data protection by calculating and storing parity information across the drives in the array.

Chained Allocation is a file allocation method where each block of data contains a pointer to the next block in the chain. This means that the blocks do not need to be contiguous in memory, allowing for more flexibility in file size and storage allocation. This method is typically used when the file size is unknown or can vary over time.

RAID 5 is characterized by distributed parity, which means that parity information is spread across all the drives in the RAID array. This allows for fault tolerance and data recovery in case of a single drive failure. Each drive in the array stores both data and parity information, ensuring that if one drive fails, the data can be reconstructed using the parity information from the remaining drives. This distributed parity scheme provides a good balance between performance, storage capacity, and fault tolerance.

RAID 6 is unique because it uses two independent distributed parity schemes. This means that the data is not only striped across multiple drives for improved performance, but also two separate parity calculations are performed and stored on different drives. This redundancy provides additional fault tolerance, as it allows for the simultaneous failure of two drives without losing any data.

A basic element of data in a file is a "field". A field is a specific piece of information within a record that holds a single value. It represents a specific attribute or characteristic of the data being stored. For example, in a database of employee records, a field could be "employee ID" or "employee name". Fields are used to organize and categorize data within a file, allowing for efficient storage and retrieval of information.

In a Pile file organization, data is collected in the order in which it arrives, and each record consists of one burst of data. This means that records are simply added to the file as they are received, without any specific order or organization. This type of file organization is simple and straightforward, but it can make it difficult to retrieve specific records or perform efficient searches.

Indexed allocation is a file allocation method where the file allocation table contains a separate one level index for each file. Each index entry corresponds to a portion of the file that is allocated on the disk. This allows for efficient file access as the index can directly point to the specific portions of the file. In contrast, in chained allocation, each file has a linked list of disk blocks, contiguous allocation allocates contiguous blocks of disk space to a file, and variable allocation allows for variable-sized disk blocks for each file.

File organization refers to the logical structuring of records. It involves arranging the data in a file in a specific manner to optimize storage and retrieval operations. This includes determining the order of records, the organization of fields within each record, and the overall structure of the file. File organization is important for efficient data management and retrieval, as it allows for faster access to specific records and reduces storage space requirements.

Chained Free Portions is the correct answer because this method requires only a pointer to the beginning of the chain and the length of the first portion. It does not need a disk allocation table, resulting in negligible space overhead. This method involves linking together the free portions of memory to form a chain, allowing efficient allocation and deallocation of memory blocks.

Rotational latency refers to the time taken for the desired sector of a disk to rotate under the disk head. This time is determined by the rotational speed of the disk and is a crucial factor in determining the overall access time of the disk. It is important because the disk head needs to wait for the desired sector to come under it before it can read or write data, and this waiting time can significantly impact the performance of the disk. Therefore, rotational latency plays a significant role in disk access and data retrieval.

The SSTF algorithm, like the SJF algorithm, may cause starvation of some requests. This means that certain requests may be continuously neglected or delayed indefinitely, leading to a lack of fairness in servicing all requests. This can occur when there are a few long-running requests that constantly arrive, causing shorter requests to be constantly pushed back and potentially never serviced.

Airline reservation systems and inventory control systems are examples of indexed systems. Indexed systems use an index or key to access and retrieve data efficiently. In the case of airline reservation systems, the index could be the flight number or passenger name, allowing quick access to relevant information. Similarly, in inventory control systems, the index could be the product code or barcode, enabling easy retrieval of inventory details. Indexed systems provide faster data retrieval compared to sequential systems, where data is accessed sequentially from the beginning.

Contiguous allocation is a preallocation strategy where variable size portions are used, and the file allocation table only requires a single entry for each file. This entry indicates the starting block and the length of the file. This strategy allows for efficient access to files as they are stored in contiguous blocks on the storage medium.

C-SCAN algorithm is a disk scheduling algorithm where the disk head moves from one end to the other, servicing requests along the way. However, unlike SCAN algorithm, when the head reaches the other end, it immediately returns to the beginning of the disk without servicing any requests on the return trip. This ensures that all the requests in the direction of the disk head movement are serviced before the head moves back to the beginning, resulting in a more efficient disk access pattern.

The Indexed Sequential file maintains the key characteristic of the sequential file by organizing records in sequence based on a key field. This means that the records are stored in a specific order according to the key field value, allowing for efficient searching and retrieval of data based on that key. The index allows for quick access to the desired records, making it a suitable choice when both sequential access and random access to the data are required.

SCAN algorithm starts at one end of the disk and moves toward the other end, servicing requests along the way. Once it reaches the other end, the direction is reversed and servicing continues. This algorithm is commonly used for disk scheduling to optimize the movement of the disk arm and reduce the average seek time.

The seek time refers to the time taken for the disk arm to move to the desired cylinder. It is the time required to position the read/write head of a disk drive to a specific track or cylinder. This time is crucial as it directly affects the overall performance of the disk drive in terms of accessing and retrieving data. The seek time is an important factor in determining the efficiency and speed of disk operations.

In the LOOK algorithm, the disk arm moves towards the final request in each direction without going to the end of the disk. It reverses direction immediately after reaching the final request, resulting in a more efficient disk scheduling algorithm compared to SCAN, C-SCAN, and C-LOOK.