04_12 DDBMS Flashcards
In a DDBMS
The software component on each computer that requests data.
transaction processor (TP) OR transaction manager (TM) OR application processor (AP)
The TP is responsible for the execution and coordination of all database requests issued by a local application that accesses data on any DP.
A data consistency model in which data changes are not immediate but propagate slowly through the system until all replicas are eventually consistent.
basically available, soft state, eventually consistent (BASE)
A data allocation strategy in which the entire database is stored at one site.
centralized data allocation (centralized database)
A hardware and software system composed of clients, servers, and middleware.
Features a user of resources and a provider of resources.
client/server architecture
The TP node that coordinates the execution of a two-phase COMMIT in a DDBMS.
coordinator
In a DDBMS
The process of deciding where to locate data fragments.
data allocation
A characteristic of a DDBMS that allows a single object to be broken into two or more segments or fragments.
The object might be a user’s database, a system database, or a table.
data fragmentation
Each fragment can be stored at any site on a computer network.
The resident software component that stores and retrieves data through a DDBMS.
data processor (DP) OR data manager (DM)
The DP is responsible for managing the local data in the computer and coordinating access to that data.
The storage of duplicated database fragments at multiple sites on a DDBMS.
Duplication of the fragments is transparent to the end user.
data replication
Data replication provides fault tolerance and performance enhancements.
A subset of a distributed database.
database fragment
Although the fragments may be stored at different sites within a computer network, the set of all fragments is treated as a single database. See also horizontal fragmentation and vertical fragmentation.
A logically related database that is stored in two or more physically indepent sites.
distributed database
A DBMS that supports a database distributed across several different sites.
distributed database management system (DDBMS)
A DDBMS governs the storage and processing of logically related data over interconnected computer systems in which both data and processing functions are distributed among several sites.
A data dictionary that contains the descriptions (fragment names and locations) of a distributed database.
distributed data catalog (DDC) OR distributed data dictionary (DDD)
The database schema description of a distributed database as seen by the database administrator.
distributed global schema
Sharing the logical processing of a database over two or more sites connected by a network.
distributed processing
A database request that allows a single SQL statement to access data in several remote DPs in a distributed database.
distributed request
A database transaction that accesses data in several remote DPs in a distributed database.
distributed transaction
A DDBMS feature that allows a distributed database to look like a single logical database to an end user.
distribution transparency
A protocol used by a DP to roll back or roll foward transactions with the help of a system’s transaction log entries.
DO-UNDO-REDO protocol
A feature that allows continuous operation of a DDBMS, even if a network node fails.
failure transparency
A DDBMS feature that allows a system to treat a distributed database as a single database even though it is divided into two or more fragments.
fragmentation transparency
A system that integrates different types of DBMS over a network.
It supports different DBMS that may even support different data models running under different computer systems.
fully heterogeneous distributed database system (fully heterogeneous DDBMS)
See also heterogeneous DDBMS and homogeneous DDBMS.
In a DDBMS
The distributed database that stores multiple copies of each database fragment at multiple sites.
fully replicated database
A feature that allows a system to integrate several centralized DBMSs into one logical DDBMS.
heterogeneity transparency
A system that integrates different types of centralized DBMS over a network.
heterogeneous DDBMS
A system that integrates only one type of centralized DBMS over a network.
homogeneous DDBMS
The distributed database design process that breaks a table into subsets of unique rows.
horizontal fragmentation
A property of a DDBMS in which database access requires the user to know both the name and location of the fragments.
local mapping transparency
A property of a DDBMS in which database access requires the user to know only the name of the database fragments.
Fragment locations need not be known.
location transparency
A combination of horizontal and vertical strategies for data fragmentation, in which a table may be divided into several rows and each row has a subset of the attributes (columns).
mixed fragmentation
A scenario describing a fully DDBMS with support for multiple data processors and transaction processors at multiple sites.
multiple-site processing, multiple-site data (MPMD)
A scenario in which multiple processes run on different computers sharing a single data repository.
multiple-site processing, single-site data (MPSD)
A data replication rule that requires all copies of data fragments to be identical.
mutual consistency rule
The delay imposed by the amount of time required for a data packet to make a round trip from point A to point B.
network latency
The delay that occurs when nodes become suddenly unavailable due to a network failure.
In distributed databases, the system must account for the possibility of this condition.
network partitioning
A database model that attempts to provide ACID-compliant transactions across a highly distributed infrastructure.
NewSQL
A distributed database in which copies of only some database fragments are stored at multiple sites.
partially replicated database
A data allocation strategy of dividing a database into two or more fragments that are stored at two or more sites.
partitioned data allocation
In partitioned databases
One or more attributes in a table that determine the fragment in which a row will be stored.
partition key
A DDBMS feature that allows a system to perform as though it were a centralized DBMS.
performance transparency
A DDBMS feature that allows a single SQL statement to access data in a single remote DP.
remote request
A DDBMS feature that allows a transaction (formed by several requests) to access data in a single remote DP.
remote transaction
The DDBMS’s ability to hide the existence of multiple copies of data from the user.
replica transparency
A data allocation strategy in which copies of one or more database fragments are stored at several sites.
replicated data allocation
A scenario in which all processing is done on a single host computer and all data is stored on the host computer’s local disk.
single-site processing, single-site data (SPSD)
In a DDBMS
A DP node that participates in a distributed transaction using the two-phase COMMIT protocol.
subordinate
A DDBMS property that ensures database transaction will maintain the distributed database’s integrity and consistency, and that a transaction will be completed only when all database sites involved complete their part of the transaction.
transaction transparency
In a DDBMS
An algorithm used to ensure atomicity of transactions and database consistency as well as integrity in distributed transactions.
two-phase commit protocol (2PC)
In a DDBMS
A condition in which each row is unique, regardless of which fragment it is located in.
unique fragment
A distributed database in which each database fragment is stored at a single site.
unreplicated database
In distributed database design
The process that breaks a table into a subset of columns from the original table.
vertical fragmentation
Fragments must share a common primary key.
A protocol that ensures transaction logs are written to permanent storage before any database data is actually updated.
write-ahead protocol
