Glossary
A
ACID Atomicity, Consistency, Isolation, and Durability. Four characteristics that a relational database must be able to maintain for transactions.
ADDM Automatic Database Diagnostic Monitor. A tool that generates performance tuning reports based on snapshots in the Automatic Workload Repository (AWR).
ADR Automatic Diagnostic Repository. The default location for the alert log, trace files, and other information useful for fault finding. An always-on facility that captures errors in trace and dump files the first and any subsequent times they occur.
ADRCI The Automatic Diagnostic Repository (ADR) command-line interface accessed using the adrci command.
AES Advanced Encryption Standard. A widely used data encryption method.
AL16UTF16 A Unicode fixed-width, 2-byte character set, commonly specified for the NLS character set used for NVARCHAR2, NCHAR, and NCLOB data types.
alias In Oracle Net, a pointer to a connect string. An alias must be resolved to the address of a listener and the name of a service or instance.
ANSI American National Standards Institute. A U.S. body that defines a number of standards relevant to computing.
API Application programming interface. A defined method for manipulating data—for example, a set of PL/SQL procedures in a package written to perform a related set of tasks.
ARBn Background processes that perform extent movement between disks in an Automatic Storage Management (ASM) disk group.
ASA Automatic Segment Advisor. An Oracle advisory tool that can recommend segments (tables or indexes) that are candidates for segment shrink.
ASCII American Standard Code for Information Interchange. A standard (with many variations) for coding letters and other characters as bytes.
ASH Active Session History. A category of information in the AWR that records details of session activity.
ASM Automatic Storage Management. A logical volume manager (LVM) provided with the Oracle database.
asmcmd A command-line utility used to query and maintain objects in an ASM disk group.
ASSM Automatic Segment Space Management. The method of managing space within segments by use of bitmaps.
attribute One element of a tuple (aka a column or field).
AWR Automatic Workload Repository. A set of tables in the SYSAUX tablespace, populated with tuning data gathered by the MMON process.
B
background process A process that is part of the instance that is launched at startup.
BFILE A large object data type that is stored as an operating system file. The value in the table column is a pointer to the file.
bind variable A value passed from a user process to a SQL statement at statement execution time.
BLOB Binary Large Object. A LOB data type for binary data such as photographs and video clips.
block The unit of storage into which datafiles are formatted. The size can be 2KB, 4KB, 8KB, 16KB, 32KB, or 64KB. Some platforms will not permit all these sizes.
BMR Block media recovery. An RMAN feature that recovers individual blocks instead of entire database objects to save time during recovery.
C
CET Central European Time. A time zone used in much of Europe (though not Great Britain) that is one hour ahead of UTC, with daylight savings time in effect during the summer months.
character set The encoding system for representing data within bytes. Different character sets can store different characters and may not be suitable for all languages. Unicode character sets can store any character.
check constraint A simple rule enforced by the database that restricts values that can be entered into a column.
checkpoint An event that forces the DBWn (database writer) process to write all dirty buffers from the database buffer cache to the datafiles.
CKPT The checkpoint process. The background process responsible for recording the current redo byte address—the point at which the DBWn has written changed data blocks to disk—and for signaling checkpoints, which force DBWn to write all changed blocks to disk immediately.
client-server architecture A processing paradigm in which the application is divided into client software that interacts with the user and server software that interacts with the data.
CLOB Character Large Object. A LOB data type for character data, such as text documents stored in the database character set.
cluster A hardware environment in which more than one computer shares access to storage. A Real Application Cluster (RAC) database consists of several instances on several computers opening one database on a shared storage device.
column An element of a row: tables are two-dimensional structures, divided horizontally into rows and vertically into columns.
commit To make a change to data permanent.
complete recovery Following a restore of damaged database files, a complete recovery applies all redos to bring the database up to date with no loss of data.
connect identifier An Oracle Net alias.
connect role A preseeded role retained only for backward compatibility. Oracle now adopts a minimal security policy at installation and database creation, allowing administrators better control over database security.
connect string The database connection details needed to establish a session: the address of the listener and the service or instance name.
consistent backup A backup made while the database is closed.
constraint A mechanism for enforcing rules on data: a column value must be unique or may contain only certain values. A primary key constraint specifies that the column must be both unique and not null.
control file The file containing pointers to the rest of the database, critical sequence information, and the RMAN repository.
CPU Central processing unit. The chip that provides the processing capability of a computer, such as an Intel Pentium or a Sun SPARC.
CTWR Change Tracking Writer. The optional background process that records the addresses of changed blocks to enable fast incremental backups.
D
data blocks The units into which datafiles are formatted, made up of one of more operating system blocks.
data dictionary The tables and views owned by SYS in the SYSTEM tablespace that define the database and the objects within it.
data dictionary views Views on the data dictionary tables that let the DBA query the state of the database.
Data Guard A facility whereby a copy of the production database is created and updated (possibly in real time), with all changes applied to the production database.
Data Pump A facility for transferring large amounts of data at high speed into, out of, or between databases.
database buffer cache An area of memory in the System Global Area (SGA) used for working on blocks copied from datafiles.
database link A connection from one database to another, based on a username and password and a connect string.
Database Replay An Oracle monitoring feature that can help to assess the change in performance on a test system by capturing the workload on a production server and replaying the workload on a test system.
datafile The disk-based structure for storing data.
DBA Database administrator. The person responsible for creating and managing Oracle databases—this could be you.
DBA role A preseeded role in the database provided for backward compatibility that includes all the privileges needed to manage a database, except the privilege needed to start up or shut down.
DBCA The Database Configuration Assistant. A GUI tool for creating, modifying, and dropping instances and databases.
DBID Database identifier. A unique number for each individual database, visible in the DBID column of the V$DATABASE dynamic performance view.
DBMS Database management system. This is often used interchangeably with RDBMS.
DBNEWID A command-line utility (usually nid) that can change the value of DBID for a database.
DBWn or DBWR The database writer. The background process responsible for writing changed blocks from the database buffer cache to the datafiles. An instance can have up to 20 database writer processes, DBW0 through DBW9 and DBWa through DBWj.
DDL Data Definition Language. The subset of SQL commands that change object definitions within the data dictionary: CREATE, ALTER, DROP, and TRUNCATE.
deadlock A situation in which two sessions block each other, such that neither can do anything. Deadlocks are detected and resolved automatically by the DIA0 background process.
DHCP Dynamic Host Configuration Protocol. The standard for configuring the network characteristics of a computer, such as its IP address, in a changing environment where computers can be moved from one location to another.
DIA0 The diagnosability process that detects hang and deadlock situations.
DIAG The diagnosability process that generates diagnostic dumps.
direct path A method of I/O on datafiles that bypasses the database buffer cache.
directory object An Oracle directory: a object within the database that points to an operating system directory.
dirty buffer A buffer in the database buffer cache that contains a copy of a data block that has been updated and not yet written back to the datafile.
DML Data Manipulation Language. The subset of SQL commands that change data within the database: INSERT, UPDATE, DELETE, and MERGE.
DMnn Data Pump Master process. The process that controls a data pump job—one will be launched for each job that is running.
DNS Domain Name Service. The TCP mechanism for resolving network names into IP addresses. Runs on a machine called a DNS server.
domain The set of values an attribute is allowed to have. Terminology: tables have rows, and rows have columns with values; or, relations have tuples, and tuples have attributes with values taken from their domain.
DSS Decision Support System. A database, such as a data warehouse, optimized for running queries with high I/O activity on large chunks of data, as opposed to online transaction processing (OLTP) work that accesses small chunks of data at a time.
DWnn Data Pump Worker process. One or more of these will be launched for each data pump job that is running.
E
easy connect A method of establishing a session against a database by specifying the address on the listener and the service name, without using an Oracle Net alias.
EBCDIC Extended Binary Coded Decimal Interchange Code. A standard developed by IBM for coding letters and other characters in bytes.
environment variable A variable set in the operating system shell that can be used by application software and by shell scripts.
equijoin A join condition using an equality operator.
F
fast incremental backup An incremental backup that uses a block change tracking file to identify only changed blocks since the last backup.
FGA Fine-grained auditing. A facility for tracking user access to data, based on the rows that are seen or manipulated.
flash recovery area A location on a file system or an Automatic Storage Management (ASM) disk group for all recovery-related files.
Flashback Data Archive A database container object that retains historical data for one or more database objects for a specified retention period.
Flashback Database A flashback feature that recovers the entire database to a point of time in the past using Flashback Database logs.
Flashback Database logs Changed database blocks that are stored in the flash recovery area and used for Flashback Database.
Flashback drop A flashback feature that makes it easy to recover dropped tables if they are still in a tablespace’s recycle bin.
Flashback Query A flashback feature that enables you to view one or more rows in a table at a time in the past.
Flashback Table A Flashback Query that recovers a single table and its associated objects to a point in time that has passed.
fractured block A database block that is simultaneously being read by an operating system copy command and modified by the DBWR process.
full backup A backup containing all blocks of the files backed up, not only those blocks changed since the last backup.
G
GMT Greenwich Mean Time. Now referred to in the United States as UTC, which is the time zone of the meridian through the Greenwich Observatory in London.
grid computing An architecture for which the delivery of a service to end users is not tied to certain server resources but can be provided from anywhere in a pool of resources, linking multiple low-cost, independently capable machines into a single, far more powerful grouped virtual platform.
GUI Graphical user interface. A layer of an application that lets users work with applications using a graphically driven screen interface, using both keyboard and mouse. The X Window System and Microsoft Windows are both GUI applications that provide GUI-driven access to other GUI applications.
H
HTTP Hypertext Transfer Protocol. The protocol that enables the World Wide Web (both invented at the European Organization for Nuclear Research in 1989). This layered protocol runs over TCP/IP.
HWM High water mark. The last block of a segment that has ever been used—blocks above this are part of the segment but are not yet formatted for use.
I
IBM International Business Machines. A well-known computer hardware, software, and services company.
image copy A Recovery Manager (RMAN) bit-for-bit copy of a file.
inconsistent backup A backup made while the database is open.
incremental backup A backup containing only blocks that have been changed since the last backup was made.
instance recovery The automatic repair of damage caused by a disorderly shutdown of the database, either from a crash or from running SHUTDOWN ABORT.
I/O Input/output. The activity of reading from or writing to disks—often the slowest point of a data processing operation because it’s the slowest piece of hardware when compared with CPU and RAM.
IOT Index-organized table. A table type in which the data rows are stored in the leaf blocks of an index segment. The table is effectively an index.
IP Internet Protocol. Together with the Transmission Control Protocol, TCP, TCP/IP is the de facto standard communication protocol used for client-server communication over a network.
IPC Inter-Process Communications protocol. The platform-specific protocol provided by your OS vendor and used for processes running on the same machine to communicate with each other.
ISO International Organization for Standardization. A group that defines many standards, including SQL.
J
job A row in a scheduler table that specifies what to do and when to do it. The “what” can be a single SQL statement, a PL/SQL block, a PL/SQL stored procedure, a Java stored procedure, an external procedure, or any executable file stored in the server’s file system.
job chain A database object that contains a named series of programs linked together for a combined objective.
job class A scheduler object that is used to associate one or more jobs with a Resource Manager consumer group and to control logging levels.
join The process of connecting rows in different tables based on common column values.
JVM Java Virtual Machine. The runtime environment needed for running code written in Java. Oracle provides a JVM that executes within the database, and another is provided by your operating system, which runs in the operating system.
L
large pool A memory structure within the System Global Area (SGA) used by certain processes, principally shared server processes and parallel execution servers.
LDAP Lightweight Directory Access Protocol. The TCP implementation of the X25 directory standard, used by the Oracle Internet Directory for name resolution, security, and authentication. LDAP is also used by other software vendors, including Microsoft and IBM.
level 0 incremental backup A full RMAN backup that can be used as the basis for an incremental backup strategy.
level 1 cumulative incremental backup An RMAN backup of all changed blocks since the last level 0 incremental backup.
level 1 differential incremental backup An RMAN backup of all changed blocks since the last level 0 or level 1 incremental backup.
LGWR Log Writer. The background process responsible for flushing change vectors from the log buffer in memory out to the online redo log files on disk.
library cache A memory structure within the shared pool that is used for caching SQL statements parsed into their executable form.
lightweight job A scheduler job that has many of the same characteristics of a standard job, except that a lightweight job is ideal for running many short-duration jobs that run frequently.
listener A server-side process that listens for database connection requests from user processes and launches dedicated server processes to establish sessions. The sessions become the connections between the user process and the database unless shared servers are in use, in which case a dispatcher process is used to share time to shared server processes.
LOB Large object. A data structure that contains a large amount of binary or character data, such as an image or a document. LOBs (Oracle supports several types) are defined as columns of a table but can be either physically stored in a separate segment or stored within the table itself.
Locale Builder A graphical tool that can create a customized globalization environment by generating definitions for languages, territories, character sets, and linguistic sorting.
log switch The action of closing one online logfile group and opening another (triggered by the LGWR process filling the first group), and then causing the now offline log file to be archived.
logical backup A backup that reads a set of database rows and writes them to a file in the operating system or to another tablespace.
LRU Least Recently Used. An algorithm in which LRU lists manage access to data structures that are used infrequently.
LVM Logical Volume Manager. A layer of software that groups physical storage areas (one or more disk partitions) all into groups or volumes. A single volume is then accessed to manage data on one or more underlying physical disks.
M
MMAN The Memory Manager background process, which monitors and reassigns memory allocations in the SGA for automatically tunable SGA components.
MML Media Management Layer. Software that lets RMAN make use of automated tape libraries and other SBT (System Backup to Tape) devices.
MMNL Manageability Monitor Light. The background process responsible for flushing Active Session History (ASH) data to the Automatic Workload Repository (AWR)—if the Manageability Monitor (MMON) is not doing this with the necessary frequency.
MMON The Manageability Monitor. A background process that is responsible for gathering performance monitoring information and raising alerts.
mounted database A condition in which the instance has opened the database controlfile, the online redo logfiles, and the datafiles.
MTBF Mean Time Between Failures. A measure of the average length of running time for a database between unplanned shutdowns.
MTS Multithreaded server. Since release 9i, renamed Shared Server. This is the technique whereby a large number of sessions can share a small pool of server processes, rather than requiring one dedicated server process each. Dedicated server processes can often be the most efficient for anything other than the most extreme types of production environments.
MTTR Mean Time To Recover. The average time it takes to make the database available for normal use after a failure.
multiplexing To maintain multiple copies of files (particularly controlfiles and redo log files). Previous versions of Oracle have used the terms multiplexing to describe controlfile duplication and duplexing to describe log file member duplications.
N
namespace A logical grouping of objects within which no two objects may have the same name.
NCLOB National Character Large Object. A LOB data type for character data, such as text documents that are stored in the alternative national database character set.
NLS National Language Support. The capability of Oracle Database to support many linguistic, geographical, and cultural environments—now usually referred to as globalization.
node A computer attached to a network.
Null The absence of a value, indicating that the value is not known, missing, or inapplicable. Null values are used in databases to save space and to avoid continually having to program zeros and space characters into empty columns in tables.
O
OC4J Oracle Containers for J2EE. The control structure provided by the Oracle Internet Application Server for running Java programs.
OCA Oracle Certified Associate.
OCI Oracle Call Interface. An API published as a set of C libraries that programmers can use to write user processes that will use an Oracle database.
OCP Oracle Certified Professional. The qualification you are working toward at the moment.
offline backup A backup made while the database is closed (completely shut down).
OLAP Online Analytical Processing. Selection-intensive work involving running very large and intensive queries against a (usually) large database. Oracle provides OLAP capabilities as an option, in addition to the standard query facilities.
OLTP Online Transaction Processing. A pattern of activity within a database typified by a large number of small, short transactions as well as small queries.
online backup A backup made while the database is open.
online redo log The files to which change vectors are streamed by the Log Writer (LGWR), recording all changes made to a database, ensuring complete recoverability.
ORACLE_BASE The root directory into which all Oracle products are installed.
ORACLE_HOME The root directory of any one particular Oracle product, within the ORACLE_BASE.
Oracle Net Oracle’s proprietary communications protocol, layered on top of an industry-standard protocol such as TCP/IP.
OS Operating system. Typically, in the Oracle environment, this will be a version of Unix (perhaps Linux) or Microsoft Windows.
P
parallelization An RMAN backup technique that allocates multiple channels, improving backup performance by executing partitioned chunks of I/O in parallel.
parse To verify syntax and convert SQL statements into a form suitable for execution.
PFILE A text-based file containing initialization parameters and initial values that are set when an Oracle instance starts.
PGA Program Global Area. The variable-sized block of memory used to maintain the state of a database session. PGAs are private to the session and controlled by the session’s server process.
physical backup A backup of the files that constitute the database.
PL/SQL Procedural Language/Structured Query Language. Oracle’s proprietary programming language, which combines procedural constructs, such as flow control and user interface capabilities, with SQL.
PMON The process monitor. The background process responsible for monitoring the state of user sessions against an instance.
primary key The column (or combination of columns), whose value(s) can be used to identify each row in a table.
program A scheduler object that provides a layer of abstraction between the job and the action it will perform; it is created with the DBMS_SCHEDULER.CREATE_PROGRAM procedure.
R
RAC Real Application Clusters. Oracle’s clustering technology that allows several instances running on different machines to open the same database files with the objectives of scalability, performance, and fault tolerance.
RAID Redundant Array of Inexpensive Disks. Technique for enhancing performance and/or fault tolerance by using a volume manager to present a number of physical disks to the operating system as a single logical disk.
RAM Random Access Memory. The chips that make up the real memory in your computer hardware, versus the virtual memory presented to software by the operating system. RAM is the second fastest piece of hardware in your computer other than your CPU.
raw device An unformatted disk or disk partition.
RBAL Rebalance process. A background process in an Automatic Storage Management (ASM) instance that coordinates disk activity for disk groups. In an RDBMS instance, RBAL performs opening and closing of the disks in the disk group.
RDBMS Relational Database Management System. This term is often used interchangeably with DBMS.
recovery catalog Tables in a database schema that contain metadata and other backup information for RMAN backups of one or more databases.
recovery window An RMAN time period that defines how far back in time the database can be recovered.
referential integrity Rules defined in a relational database between primary and foreign keys, where the primary key must exist in a table for a row to exist on a subset table (in the foreign key) and defines one-to-many relationships.
relation A two-dimensional structure consisting of tuples with attributes (aka a table).
resource consumer groups Groups of users or sessions that have similar resource needs.
Resource Manager An Oracle feature that can allocate resources based on CPU usage, degree of parallelism, number of active sessions, undo space, CPU time limit, and idle time limit.
resource plan A set of rules in Resource Manager that assign various resources at specific percentages or relative priorities to a resource group.
resource plan directives Rules within Resource Manager that associate consumer groups with a resource plan and specify how the resources are divided among the consumer groups or subplans.
restore point A database object containing either a System Change Number (SCN) or a time in the past used to recover the database to the SCN or timestamp.
Resumable Space Allocation An Oracle feature that suspends instead of terminating large database operations that require more disk space than is currently available. A suspended operation can be restarted from where it stopped at a later point in time, when the space issues have been resolved. It saves time.
retention policy The number of copies of all objects that RMAN will retain for recovery purposes.
RMAN Recovery Manager. Oracle’s backup and recovery tool.
ROWID The unique identifier of every row in the database, which is used as a pointer to the physical location of the row from logical objects such as tables and indexes. The rowid data type is proprietary to Oracle Corporation and is not part of the SQL standard, and it is not recommended for direct storage into tables because the values can change.
RVWR The Recovery Writer background process is an optional process responsible for flushing the flashback buffer to the flashback logs.
S
SBT System backup to tape. An RMAN term for a tape device.
schedule A specification for when and how frequently a job should run.
schema The objects owned by a database user; synonymous with a user from a physical perspective. A schema is a user that is used to store tables and indexes. Users are created to access that schema user as multiple application users of that centrally managed schema.
SCN System Change Number. The continually incrementing number used to track the sequence and exact time of all events within a database.
segment A database object within a schema that stores data.
segment shrink A database operation that makes the free space in the segment available to other segments in the tablespace by compacting the data blocks in a segment.
sequence A database object within a schema that can generate consecutive numbers.
service name A logical name registered by an instance with a listener, which can be specified by a user process when it issues a connect request. A service name will be mapped onto a System Identifier (SID) by the listener when it establishes a session.
session A user process (application) connected through a server process that is connected to the instance.
SGA System Global Area. The block of shared memory that contains the memory structures that make up an Oracle instance.
SID 1. System identifier. The name of an instance that must be unique on the computer on which the instance is running. Users can request a connection to a named SID or to a logical service and let the listener choose an appropriate SID. 2. Session identifier. The number used to uniquely identify a session that is logged on to an Oracle instance.
SMON The System Monitor. The background process responsible for opening a database and monitoring the instance.
SPFILE The server parameter file. The file containing the parameters used to build an instance in memory. This is a binary form of the parameter file. A text form of the parameter file is called the PFILE.
SQL Structured Query Language. An international standard language for extracting data from and manipulating data in relational databases.
SQL Tuning Advisor An Oracle advisor that performs statistics analysis, SQL Profile analysis, access path analysis, and structure analysis.
synonym A pointer (named reference) to a database object, typically used to avoid fully qualified names for schema objects.
SYSASM A system privilege in an ASM instance that facilitates the separation of database administration and storage administration.
SYSDBA The privilege that lets a user connect with operating system or password file authentication and create, start up, and shut down a database.
SYSOPER The privilege that lets a user connect with operating system or password file authentication and start up and shut down (but not create) a database.
SYSTEM A preseeded schema used for database administration purposes.
T
table A logical two-dimensional data storage structure, consisting of rows and columns.
tablespace The logical structure that abstracts logical data storage in tables from physical data storage in datafiles.
TCP Transmission Control Protocol. Together with the Internet Protocol, IP, TCP/IP is the de facto standard communication protocol used for client-server communication over a network.
TCPS TCP with SSL. The secure sockets version of TCP.
tempfile The physical storage that makes up a temporary tablespace that is used for storing temporary segments.
TNS Transparent Network Substrate. The heart of Oracle Net, a proprietary layered protocol running on top of whatever underlying network transport protocol you choose to use—probably TCP/IP.
transaction A logical unit of work, which will complete in total or not at all.
TSPITR Tablespace Point In Time Recovery. A recovery method that is ideal for recovering a set of objects isolated to a single tablespace.
tuple A one-dimensional structure consisting of attributes (aka a row).
U
UGA User Global Area. The part of the Program Global Area (PGA) that is stored in the System Global Area (SGA) for sessions running through shared servers.
UI User interface. The layer of an application that communicates with end users; nowadays, the UI is frequently graphical—a GUI.
URL Uniform Resource Locator. A standard for specifying the location of an object on the Internet (a web site name you type into your browser), consisting of a protocol, a host name and domain, an IP port number, a path and filename, and a series of parameters.
user managed recovery Recovery using tools or commands outside of RMAN, used to recover a database or tablespace.
UTC Coordinated Universal Time, previously known as Greenwich Mean Time (GMT). UTC is the global standard time zone. All other time zones relate to it as offsets, which are ahead of or behind UTC.
V
virtual private catalog A logical partitioning of an RMAN catalog to facilitate separation of duties among several DBAs.
W
whole database backup A database backup that includes all datafiles plus the control file.
window A scheduler construct that extends the concept of schedules by giving Oracle more freedom on deciding when to run a job within a specific start and begin time—for a single day or every day of the week.
X
X As in the X Window System, the standard GUI environment used on most non–Microsoft Windows computers.
XML Extensible Markup Language. A standard for data interchange using documents, in which the format of the data is defined by tags within the document.