Oracle Glossary

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Oracle Cloud

Data center

A facility used to house computer systems and associated components.
Oracle provides data centers in various geographical regions. An identity domain and the services associated with that domain must belong to a specific data center.

Data region

A geographical region that’s associated with one or more data centers. When you sign up for an Oracle Cloud account, you select a default data region, where your services will be hosted.

Identity domain

A domain that controls the authentication and authorization of the users who can sign in to an Oracle Cloud service and which features they can access.
An Oracle Cloud service in a traditional cloud account must belong to an identity domain.

Oracle Account

Oracle Account is a unique customer account and can correspond to an individual, an organization, or a company that is an Oracle customer.
This account gives you access to the website, which includes your access to applications, communities, and Oracle Technology Network (OTN).
Note the following:
An Oracle Account is different from an Oracle Cloud Account that you use to access your cloud services.

For Oracle Infrastructure as a Service (Oracle IaaS) or Oracle Platform as a Service (Oracle PaaS) offerings, an Oracle account is no longer required if you’re signing up for the Free Oracle Cloud Promotion or for a new Oracle Cloud account.

An Oracle Account is required if you’re using Oracle Store to purchase services or if you sign up for certain traditional metered Oracle PaaS offerings that are part of the Free Oracle Cloud Promotion.

An Oracle Account is also required when logging support or service requests in My Oracle Support.

Oracle Cloud account

Use this account to access your cloud services and to sign in to the Infrastructure Classic Console or Applications Console, where you manage your account and your services.
There are two types of Oracle Cloud accounts: traditional cloud accounts (also known as Cloud Service accounts) and cloud accounts with Oracle Identity Cloud Service.


A Software offered in Oracle Cloud

Service console

Service entitlements represent the right to use Oracle Cloud services, based on the resources you’ve purchased or the rights assigned to you by your Cloud Account administrator.

Service Entitlement

Service entitlements represent the right to use Oracle Cloud services, based on the resources you’ve purchased or the rights assigned to you by your Cloud Account administrator.

Service instance

The existence of a cloud service, for example, an instance of Oracle Java Cloud Service

Service instance URL

The web address (URL) that you use to access a provisioned service instance.

Service name

A name assigned to your Oracle Cloud service. The service name must be unique in the identity domain. You can add a longer description to help you identify the service after it’s activated.

Service notification

An event reported on the Infrastructure Classic Console or Applications Console in the Message center. Notifications provide information about upcoming events such as system outages or blackouts, service maintenance, promotion expiry, or resource quota breach.

Oracle Database

Access Driver

In the external table infrastructure, the API that interprets the external data for the database. The access driver runs inside the database, which uses the driver to read the data in the external table.

Access Path

The means by which data is retrieved from a database. For example, a query using an index and a query using a full table scan use different access paths.

Active Transaction

A transaction that has started but not yet committed or rolled back.


Automatic Database Diagnostic Monitor. An Oracle Database infrastructure that enables a database to diagnose its own performance and determine how identified problems


Automatic Diagnostic Repository. A a file-based hierarchical data store for managing diagnostic information, including network tracing and logging.

Alert log

A file that provides a chronological log of database messages and errors. The alert log is stored in the ADR.


A join that returns rows from the left side of the predicate for which there are no corresponding rows on the right side of the predicate.

Application Architecture

The computing environment in which a database application connects to an Oracle database. The two most common database architectures are client/server and multitier.

Application Domain Index

A customized index specific to an application.

Archived Redo log file

A member of the online redo log that has been archived by Oracle Database. The archived redo log files can be applied to a database backup in media recovery.


A mode of the database that enables the archiving of the online redo log.

Ascending Index

An index in which data is stored in ascending order. By default, character data is ordered by the binary values contained in each byte of the value, numeric data from smallest

Automatic undo Management mode

A mode of the database in which it automatically manages undo space in a dedicated undo tablespace.

See also manual undo management mode.


Automatic Workload Repository (AWR). A built-in repository in every Oracle database. Oracle Database periodically makes a snapshot of its vital statistics and workload information and stores them in AWR.

B-tree index

An index organized like an upside-down tree. A B-tree index has two types of blocks: branch blocks for searching and leaf blocks that store values. The leaf blocks contain every indexed data value and a corresponding rowid used to locate the actual row. The “B” stands for “balanced” because all leaf blocks automatically stay at the same depth.

Background Process

A process that consolidates functions that would otherwise be handled by multiple Oracle programs running for each client process. The background processes asynchronously perform I/O and monitor other Oracle processes.

Bind Variable

A placeholder in a SQL statement that must be replaced with a valid value or value address for the statement to execute successfully. By using bind variables, you can write a SQL statement that accepts inputs or parameters at run time. The following example shows a query that uses v_empid as a bind variable:

SELECT * FROM employees WHERE employee_id = :v_empid;

Bitmap join index

A bitmap index for the join of two or more tables.

Bitmap merge

An operation that merges bitmaps retrieved from bitmap index scans. For example, if the gender and DOB columns have bitmap indexes, then the database may use a bitmap merge if the query predicate is WHERE gender=’F’ AND DOB > 1966.

Block header

A part of a data block that includes information about the type of block, the address of the block, and sometimes transaction information.

Block overhead

Space in a data block that stores metadata required for managing the block. The overhead includes the block header, table directory, and row directory.

Branch block

In a B-tree index, a block that the database uses for searching. The leaf blocks store the index entries. The upper-level branch blocks of a B-tree index contain index data that points to lower-level index blocks.


A main memory address in the database buffer cache. A buffer caches currently and recently used data blocks read from disk. When a new block is needed, the database can replace an old data block with a new one.

Byte semantics

Treatment of strings as a sequence of bytes. Offsets into strings and string lengths are expressed in bytes.

Cache recovery

The phase of instance recovery where Oracle Database applies all committed and uncommitted changes in the online redo log files to the affected data blocks.


The ratio of distinct values to the number of table rows. A column with only two distinct values in a million-row table would have low cardinality.

Character encoding

A code that pairs each character from a given repertoire with a code unit to facilitate data storage.

Character semantics

Treatment of strings as a sequence of characters. Offsets into strings and string lengths are expressed in characters (character codes).

Character set

An encoding scheme used to display characters on your computer screen.


1. A data structure that marks the checkpoint position, which is the SCN in the redo thread where database instance recovery must begin. Checkpoints are recorded in the control file and each data file header, and are a crucial element of recovery.

2. The writing of dirty data blocks in the database buffer cache to disk. The database writer (DBW) process writes blocks to disk to synchronize the buffer cache with the data files.

Client process

A process that executes the application or Oracle tool code. When users run client applications such as SQL*Plus, the operating system creates client processes to run the applications.

Client/server architecture

Software architecture based on a separation of processing between two CPUs, one acting as the client in the transaction, requesting and receiving services, and the other as the server that provides services in a transaction.

Cluster file system

A distributed file system that is a cluster of servers that collaborate to provide high performance service to their clients.

Cluster index

A B-tree index on the cluster key.

Cluster key

In a table cluster, the column or columns that the clustered tables have in common. For example, the employees and departments tables share the department_id column. You specify the cluster key when creating the table cluster and when creating every table added to the table cluster.


Vertical space in a table that represents a domain of data. A table definition includes a table name and set of columns. Each column has a name and data type.


Action that ends a database transaction and makes permanent all changes performed in the transaction.

Composite index

An index on multiple columns in a table.

Composite partitioning

In partitioning strategy in which a table is partitioned by one data distribution method and then each partition is further divided into subpartitions using a second data distribution method.

Compression unit

In Hybrid Columnar Compression, a logical construct that stores a set of rows. When you load data into a table, the database stores groups of rows in columnar format, with the values for each column stored and compressed together. After the database has compressed the column data for a set of rows, the database fits the data into the compression unit.


Simultaneous access of the same data by many users. A multiuser database management system must provide adequate concurrency controls so that data cannot be updated or changed improperly, compromising data integrity.