Unit 2 Written Assignment
Transaction Deadlock
CS3306 Databases 2
University of the People
Introduction In a multi-process system, deadlock is an unwanted situation that arises in a shared resource environment, where a process indefinitely waits for a resource that is held by another process. A deadlock occurs when two or more tasks permanently block each other by each task having a lock on a resource which the other tasks are trying to lock. When a detection algorithm determines that a deadlock exists, the system must recover from the deadlock. The most common solution is to roll back one or more transactions to break the deadlock.
There are solutions to dealing with deadlock: Selection of a victim, Rollback and
…show more content…
The simplest solution is a total rollback, which aborts the transaction and then restart it. However, it is more effective to roll back the transaction only as far as necessary to break the deadlock. This is known as a partial rollback which requires the system to maintain additional information about the state of all the running transactions. The sequence of lock requests or grants and updates performed by the transaction needs to be recorded. The deadlock detection mechanism should decide which locks the selected transaction needs to release in order to break the deadlock. The selected transaction must be rolled back to the point where it obtained the first of these locks, undoing all actions it took after that point. The recovery mechanism must be capable of performing such partial rollbacks. Furthermore, the transactions must be capable of resuming execution after a partial rollback (Silberschatz, Korth & Sudarshan, …show more content…
Starvation Starvation can occur in systems where the selection of victims is based primarily on cost factors, that is, there is a high possibility that the same transaction is always picked as a victim. The downside to this is that this transaction may never get to complete its designated task, leading to the issue of starvation. Therefore, mechanisms must be put in place to ensure that transaction can be picked as a victim only a (small) finite number of times. Including the number of rollbacks in the cost factor is a common strategy used to deal with the issue.
Conclusion
The graph in figure 16.18 does not have any cycles and therefore it is not in a deadlock state. However, connecting T28 to T27 will create a cycle and thus a deadlock state. Each transaction (T26, T27 and T28) will now be dependent each other because one transaction will have a lock on sources that will be needed by the next transaction and so on. Deadlocks should be prevented. Mechanisms should be put in place to detect deadlocks and to correct them as soon as
Fault tolerance is the property that enables a system to continue operating properly in the event of a failure.
Write generic instructions to compute (p + q) / (r - p) + p * (r – q) using a processor that supports:
In politics, gridlock or deadlock or political stalemate refers to a situation when there is difficulty of passing laws in a legislature because the voters for and against a proposed law are evenly divided; or in which two legisl...
According to the European Commission’s MIFID II proposal, the trading venues should also test their systems to check if they are resilient to increased order flows and also place circuit breakers to halt trading if there are unusual price movements.
Queues becoming an integral part of the Database, therefore allowing Applications to be loosely connected via Queued messages.
...ve the plan in order to mitigate down time for future events (Notes W3 P24, CGC1 P N-2).
In networking protocols layers a lot of data is transferred between different processes across a heterogeneous network. Also lot of resources are shared like bandwidth of links or the routers in buffers, where there can be many packets which are queued for transmitting from different processes. It can happen that too many packets are on same link and the queue overflows where packets can be lost or even they need to be dropped. Thus to avoid this congestion resource allocation is done.
During this problem happen, there were 100 million transaction is being effected. The deleted information is reenter back to the bank computer system. This problem is take time to solve it. Because of this problem, the bank is promises to all the customer that being effected by this problem that they will reimburse the fires and the late payment f...
Suppose that there are no shared copies of location X. If processor P1 reads location X the memory sends a copy together with a chain termination (CT) and keeps a pointer to P1. Subsequently, when processor P2 reads location X, the memory sends a copy to the cache of processor P2 along with a pointer to the cache of processor P1. If processor P3 writes to location X, it is necessary to send a data invalidation message down the chain. To ensure sequential consistency, the memory module denies processor P3 write permission until the processor with the chain termination acknowledges the invalidation of the chain.
Virtualization technologies provide isolation of operating systems from hardware. This separation enables hardware resource sharing. With virtualization, a system pretends to be two or more of the same system [23]. Most modern operating systems contain a simplified system of virtualization. Each running process is able to act as if it is the only thing running. The CPUs and memory are virtualized. If a process tries to consume all of the CPU, a modern operating system will pre-empt it and allow others their fair share. Similarly, a running process typically has its own virtual address space that the operating system maps to physical memory to give the process the illusion that it is the only user of RAM.
When an executable file is loaded into memory, it is called a process. A process is an instance of a program in executing. It contains its current activity, such as its program code and also the contents of the processor’s register. It generally includes the process stack, which contain temporary data, and a data section, which global variables. During runtime, it may include a heap, or dynamically allocated memory. In contrast with a program, a process is “an active entity, with a program counter specifying the next instruction to execute and a set of associated resources” (Operating System Concept 106). A process is a program that executes a single instance of a thread. Multiple threads can exist which allows more than one task to perform at a time. Multithreaded processes may share resources such as code, data, and file section. They do not share resources such as registers and stack.
Parallel event may occur in multiple resources during the same time interval and pipelined event may occur in overlapped time spans.
Reader and writer problem are examples of computer simultaneously there are three type of problem which handle many threads which are try to reach or access the resources at the same time in these threads some may able to read and some are writes with constraint no one process can access the recourses which is shared while it’s writing or reading and other process perform writing to it. Data structure of the writer and reader locks resolve the problem of reader and writer. Reader can only read data set and cannot update is done by the writer. And writer can both read and write.
In today’s world, computers are becoming more relevant than ever before. With this comes hardtack. Anyone who uses computers must experience some sort of frustration at some time. There is really no way around it. This may include all or some of the error messages, unanticipated results because of the software, or having a computer just freeze up for no apparent reason.
In HDLs, the problem of parallel updates to a shared resource is solved by updating only one “process” and exactly one possible new value for x is specified for every clo...