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...
by admin | Jun 6, 2015 | sem3
Dynamic Hashing The problem with static hashing is that it does not expand or shrink dynamically as the size of the database grows or shrinks. Dynamic hashing provides a mechanism in which data buckets are added and removed dynamically and on-demand. Dynamic hashing...
by admin | Jun 6, 2015 | sem3
Static Hashing STATIC HASHING In static hashing, when a search-key value is provided, the hash function always computes the same address. For example, if mod-4 hash function is used, then it shall generate only 5 values. The output address shall always be same for...
