1 Data Files: This is where the data is stored. 2 Data Dictionary: This is a collection of information on the structure of any database object. The metadata is governed by the repository of information. 3 Indices - It allows for quicker data retrieval. There are three main types of indices: B-tree, Hash, and R-tree.
A Data Catalog is a collection of metadata paired with data management and search capabilities that assists analysts and other data users in finding the data they want, serves as an inventory of accessible data, and gives information to evaluate the fitness of data for intended applications. The Data Catalog is also called a "Data Bank" or "Data Warehouse".
The importance of a good Data Catalog is that it provides a central location where data users can find relevant information about their data sets. This helps them decide what data to load into their systems and which data sources to use when there is more than one option available. A good Data Catalog also saves time for data users because they no longer have to hunt down each piece of information themselves. They can simply ask Google or another data source to give them the answer instead.
In addition to these benefits, having a good Data Catalog ensures that your organization's data assets are well managed and organized. This helps ensure that you do not lose track of any important files and that everyone has access to the same data. It also prevents duplicate entries of data items such as names or codes which would otherwise lead to errors during data import or analysis processes.
Last but not least, having a good Data Catalog is necessary for ensuring data quality. A good Data Catalog contains information on how each data set was created and by whom.
A relational database's data tables hold information about connected items. Each row has a record with a unique identifier – known as a key – and each column contains data characteristics. Each record assigns a value to each characteristic, making it simple to establish correlations between data points. The result is that a relational database can easily store and retrieve sets of data that may not be easy or possible in other ways.
A relational database uses relations to connect information between its rows. A relation is a set of pairs of values, where both values come from the same domain and are associated by some relationship. In other words, a relation is a collection of ordered pairs of domain elements that define an association between them. For example, the names "John" and "Mary" together with the word "love" form a relation because they all belong to the same domain (humans) and there is an order to these pairs (i.e., name-value).
In mathematics, a relation is defined as a subset of a cartesian product. That is, a relation is a collection of ordered pairs. In computer science, a relation is a mapping of fields from one set into another. In this case, the domain is the set of all human beings, while the range is the set of all loves that they have given or received. A relation can also be described as a table with multiple columns from which certain cells contain only one value, whereas others contain many values.
Datafiles, redo log files, and control files make up the physical database structure. Datafiles The data in a database is stored in datafiles. The data of logical data structures like tables and indexes is stored in the database's datafiles. A tablespace is a logical unit of database storage made up of one or more datafiles...
Redo log files Redo logs contain information about what changes were made to the database while it was offline so that they can be applied when the database comes back on-line. They are needed for concurrency control because two users cannot see each other's changes until these changes are written to the redo log. The default size of the redo log is 80 percent of the space available at the end of the last checkpoint; however, you can increase or decrease its size with the REDO_LOG parameter...
Control files Control files contain information about the status of objects in the database. For example, if you delete an object from the database, then the control file would record this fact. Control files also contain information necessary to rebuild indexes or tables after their definition has changed. Control files are used by the Database Administration Tool (DBCC) to perform various consistency checks as well as repair problems with the database. DBCC controls are described in detail in Chapter 21.
The control files are divided into sections called control blocks. Each section contains records indicating the current state of objects within that portion of the database.
Aspects of a Relational Database
A Database's Elements
The property that specifies the type of data that may be placed in a field, such as integers, text, or dates. Database A structured collection of information about people, events, objects, or ideas relating to a certain topic or goal. The term database is used for collections of information which are stored together electronically. These databases can be organized in any way and contain any amount of information.
The word "database" comes from Latin datum meaning given or appointed and basis, which means a foundation or basis. In computer science, a database is a structured collection of information stored in a computer system. Databases provide a flexible and efficient way to store and organize information for rapid retrieval.
A database can be as small as a list of names or addresses kept in a personal organizer, or it can be a large electronic repository containing information about people, such as those found in social networking sites. The latter type of database is often called a "social network". Data within these databases may include information about products, services, or deals available from companies, records of calls made or emails sent by users, demographic information about people using the site, and so on.
Data storage is the process of saving data into a database. Data storage can be done manually, automatically, or with the use of a middleware component. Data storage determines the size of your database.