by admin | Jun 6, 2015 | sem3
Deadlock 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. For example, assume a set of transactions {T0, T1, T2, …,Tn}....
by admin | Jun 6, 2015 | sem3
Two Phase Commit Protocol Two-Phase Locking 2PL This locking protocol divides the execution phase of a transaction into three parts. In the first part, when the transaction starts executing, it seeks permission for the locks it requires. The second part is where the...
by admin | Jun 6, 2015 | sem3
Lock-based Protocols Database systems equipped with lock-based protocols use a mechanism by which any transaction cannot read or write data until it acquires an appropriate lock on it. Locks are of two kinds − Binary Locks − A lock on a data item can be in two states;...
by admin | Jun 6, 2015 | sem3
Concurrency Control In a multiprogramming environment where multiple transactions can be executed simultaneously, it is highly important to control the concurrency of transactions. We have concurrency control protocols to ensure atomicity, isolation, and...
by admin | Jun 6, 2015 | sem3
Serializability Serializability is the classical concurrency scheme. It ensures that a schedule for executing concurrent transactions is equivalent to one that executes the transactions serially in some order. It assumes that all accesses to the database are done...
by admin | Jun 6, 2015 | sem3
Properties of Transactions A transaction can be defined as a group of tasks. A single task is the minimum processing unit which cannot be divided further. Let’s take an example of a simple transaction. Suppose a bank employee transfers Rs 500 from A’s account to...
