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Record locking is the technique of preventing simultaneous access to data in a database, to prevent inconsistent results.. The classic example is demonstrated by two bank clerks attempting to update the same bank account for two different transactions.
For this example it is assumed that each book has only one author. A table that conforms to the relational model has a primary key which uniquely identifies a row. In our example, the primary key is a composite key of {Title, Format} (indicated by the underlining):
Examples of such operations are requesting a read operation, reading, writing, aborting, committing, requesting a lock, locking, etc. Often, only a subset of the transaction operation types are included in a schedule. Schedules are fundamental concepts in database concurrency control theory. In practice, most general purpose database systems ...
The 1-minute rule: cache sequentially accessed disk pages that are re-used every 1 minute or less. Although the 5-minute rule was invented in the realm of databases, it has also been applied elsewhere, for example, in Network File System cache capacity planning. [6] The original 5-minute rule was derived from the following cost-benefit ...
An example is a group of people calling to order a product. Highest Value PT = 1/VT — The deadline is not important. Some transactions should get to CPU based on criticalness, not fairness. This is an example of least slack that can wait the least amount of time. If the telephone switchboards were overloaded, people who call 911 should get ...
Denormalization is a strategy used on a previously-normalized database to increase performance. In computing, denormalization is the process of trying to improve the read performance of a database, at the expense of losing some write performance, by adding redundant copies of data or by grouping data.
Database administration is the function of managing and maintaining database management systems (DBMS) software. Mainstream DBMS software such as Oracle, IBM Db2 and Microsoft SQL Server need ongoing management. As such, corporations that use DBMS software often hire specialized information technology personnel called database administrators or ...
A federated database system (FDBS) is a type of meta-database management system (DBMS), which transparently maps multiple autonomous database systems into a single federated database. The constituent databases are interconnected via a computer network and may be geographically decentralized. Since the constituent database systems remain ...