Can you help me with question 12 A reader-writer lock is useful whenA) there are a significantly large number of processes attempting to enter acritical section.B) there are a significantly large number of consumer processes attempting toread data from a bounded buffer.C) there are a significantly small number of reader processes attempting to read inthe critical section.D) there are a significantly large number of reader processes attempting to read inthe critical section.

D) There are a significantly large number of reader processes attempting to read in the critical…

Answered: A reader-writer lock is useful when A)…

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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The definition of a schedule assumes that operations can be totally orderedby time. Consider a database system that runs on a system with multiple processors,where it is not always possible to establish an exact ordering betweenoperations that executed on different processors. However, operations on adata item can be totally ordered.Does this situation cause any problem for the definition of conflict serializability?Explain your answer.
Case Study: You are a graduate student working in a lab where data are accumulated for the purposes of measuring theoptical absorption of a variety of samples. For each sample there is a large data file stored on a computerin the lab. In reviewing a lab notebook from one of your predecessors in the lab and comparing that to datapublished by the lab, you find a gap. That is, some of the data that were published are not accounted for in the lab notebook. Furthermore, you are unable to locate the computer files for this missing data. You talk to a fellow graduate student about this situation, and he tells you that you should be very concerned about the situation and that it should be reported. Q. What are some possible situations that could explain the “missing” data, and how should you proceed for each?
Consider a file of 16384 records. Each record is 32 bytes long and its key field is of size 6 bytes. The file is ordered on a non-key field, and the file organization is unspanned. The file is stored in a file system with block size 1024 bytes, and the size of a block pointer is 10 bytes. If the secondary index is built on the key field of the file, and a multilevel index scheme is used to store the secondary index, the number of first-level and second-level blocks in the multilevel index are respectively
10. Consider a file F to be shared by N processes. Each process i has ID i (1 <= i <= N). The file can be accessed concurrently by multiple processes, if the sum of the IDs of these processes is less than or equal to M. a) Write a monitor that will control access to the file. That means the monitor will implement two functions, request() and release(), that will be called by a process that would like to access the file. You also need to define the monitor variables required for the solution. A process will call the request() function before accessing the file and release() function when it has finished accessing the file. b) This time implement the request() and release() functions using mutex and condition variables (like POSIX Pthreads mutex and condition variables). You need to define some global variables as well to implement these functions.
Transaction management deals with the problems of always keeping the database in a consistent state even when concurrent accesses and failures occur. Isolation requires that each transaction sees a consistent database at all times and that an executing transaction cannot reveal its results to other concurrent transactions before its commitment. ANSWER If two concurrent transactions access a data item that is being updated by one of them, it is not possible to guarantee that the second will read the correct value. Dirty reads and nonrepeatable reads may occur when one transaction can see intermediate results of another transaction before it has been committed.. Given below are two concurrent transactions T1 and T2 whose balances of amount x (balx) were recorded at times t, between t₁ and tg. As shown in the table below: If these two transactions interfere with each other, fill in the table below by selecting from the drop down list the values of balance X (bal,) at specified times…
A multi-user database system is used to support the customer payment operations of a XYZ store. Unfortunately, the system currently does not enforce concurrent control on transactions accessing and updating the data. A particular customer had a balance due of HK$ 300 when the following three transactions related to the customer were processed at the same time: (i) Payment of HK$ 300; (ii) Purchase on credit of HK$ 150; and (iii) Merchandise return (credit) of HK$ 100. Each of the three transactions read the customer record when the balance was HK$ 300. That is, all transactions have read the record before any of them was completed. The updated customer record was returned from the transactions to the database in the order of first (i), then (ii) and finally (iii). (a) After the last transaction was completed, what balance will be recorded for the customer? (b) What balance should be actually recorded for the customer after the three transactions have been processed?
In the event of an impasse, it becomes necessary to terminate said processes, thereby leading to the subsequent consequences:
A deadlock occurs when a group of processes is stalled because one process is holding a resource and waiting for another process to obtain it. Consider the situation when two trains are approaching each other on the same track and there is only one track: once they are in front of each other, neither train can proceed. In operating systems, a similar scenario happens when two or more processes possess certain resources while waiting on resources owned by other processes (s). In the picture below, Process 1 is holding Resource 1 and waiting for Process 2 to acquire Resource 2, while Process 2 is waiting for Resource 1. Give an example of a realistic deadlock avoidance approach and describe the basic strategy behind it.
In a database transaction, the two main operations are READ and WRITE operations. So, there is a need to manage these two operations in the concurrent execution of the transactions as if these operations are not performed in an interleaved manner, and the data may become inconsistent. Consider the following scheduled transactions T1, T2, T3, and T4. T1 T2 T3 T4 Reads(X) Writes(X) Reads(Y) Writes(Y) Commit Reads(X) Time Reads(X) Writes(X) Reads(Y) Rollback Writes(Y) Writes(X) Commit • Identify all pair of transactions based on the occurred problem between two transactions (specify pairs, e.g., T1 => T2; T3=> T2; T3 =>T4; etc.). • Specify the name of a problem for each detected pair of transactions. • Justify the occurred problem for each pair of transactions.
When dose buffer overflows occur Buffer overflows occurs when we do not properly account for the size of the data input into an application. When there is an escalation of privilege in an application When there is no appropriate authentication mechanism When authorization is not implemented on a given application.
Minix Attributes associated with a file can be maintained in several places as discussed inthe course content:a. Within the set of open file descriptorsb. Within the system-wide file table entry for the filec. Within the ‘i-node’ (or ‘v-node’)These attributes can be associated with the actual file (e.g. the file size), or can be associatedwith an open instance of the file (e.g. whether the file is opened for reading or writing, whether thefile is opened for non-blocking I/O, etc.).What would be preferred location of the following attributes of a file and why? Discuss anytradeoffs if that attribute could be in more than one of the above.a. The owner of the file.b. The “read/write” pointer of the open file.c. Whether the file is opened for reading, writing, or both.
1.In the Readers-Writers problem, more than one writer can access the buffer at the same time to write True False 2.Given that processes P1 and P2 are using semaphores to lock resources, determine whether or not the following sequence of requests results in a deadlock. Initially, all resources are available. P1: P2: wait(A) wait(C) wait(B) wait(B) ... .... signal(A) signal(B) signal(B) signal(C) Yes No Insufficient information 3.If no process is executing in its critical section and there exist some processes that wish to enter their critical section, then the selection of the processes that will enter the critical section next cannot be postponed indefinitely. Which option describe best Mutual Exclusion Progress Bounded Waiting None of the above 4.In the producer-consumer problem, the "out" will be used to point to the index in the buffer where a producer can produce next. True False 5.Entry section and Exit section in the code together are referred to as a solution for…

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