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SQL - Structured Query Language - Glossario da biblioteca do DB2


Volta ao Menu Principal


Desenvolvido por DORNELLES Carlos Alberto - Analista de Sistemas - Brasília DF.

As seguintes condições e abreviações estão definidas como elas são usados na biblioteca do DB2. Se você não achar o termo que está procurando, recorra a um dicionário de computação.

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Letra A

abend. Abnormal end of task.

abend reason code. A 4-byte hexadecimal code that uniquely identifies a problem with DB2. A complete list of DB2 abend reason codes and their explanations is contained in Messages and Codes.

abnormal end of task (abend). Termination of a task, a job, or a subsystem because of an error condition that cannot be resolved during execution by recovery facilities.

access method services. A utility program that defines and manages VSAM data sets (or files).

access path. The path used to get to data specified in SQL statements. An access path can involve an index or a sequential search.

active log. The portion of the DB2 log to which log records are written as they are generated. The active log always contains the most recent log records, whereas the archive log holds those records that are older and no longer will fit on the active log.

active member state. A state of a member of a data sharing group. An active member is identified with a group by XCF, which associates the member with a particular task, address space, and MVS system. A member that is not active is failed or quiesced.

alias. An alternate name that can be used in SQL statements to refer to a table or view in the same or a remote DB2 subsystem.

allied thread. A thread originating at the local DB2 subsystem that may access data at a remote DB2 subsystem.

allocated cursor. A cursor defined for stored procedure results sets by using ALLOCATE CURSOR.

already verified. An LU 6.2 security option which allows DB2 to provide the user's verified authorization ID when allocating a conversation. The user is not validated by the partner DB2.

ambiguous cursor. A database cursor that is not defined with either the clauses FOR FETCH ONLY or FOR UPDATE OF, is not defined on a read-only result table, is not the target of a WHERE CURRENT clause on an SQL UPDATE or DELETE statement, and is in a plan or package that contains SQL statements PREPARE or EXECUTE IMMEDIATE.

American National Standards Institute (ANSI). An organization consisting of producers, consumers, and general interest groups, that establishes the procedures by which accredited organizations create and maintain voluntary industry standards in the United States.

ANSI. American National Standards Institute.

API. Application programming interface.

APPL. A VTAM network definition statement used to define DB2 to VTAM as an application program using SNA LU 6.2 protocols.

application. A program or set of programs that perform a task; for example, a payroll application.

application plan. The control structure produced during the bind process and used by DB2 to process SQL statements encountered during statement execution.

application process. The unit to which resources and locks are allocated. An application process involves the execution of one or more programs.

application program interface (API). A functional interface supplied by the operating system or by a separately orderable licensed program that allows an application program written in a high-level language to use specific data or functions of the operating system or licensed program.

application requester (AR). See requester.

application server. See server.

AR. application requester. See requester. archive log. The portion of the DB2 log that contains log records that have been copied from the active log.

AS. Application server. See server.

ASCII. An encoding scheme used to represent strings in many environments, typically on PCs and workstations. Contrast with EBCDIC.

attachment facility. An interface between DB2 and TSO, IMS, CICS, or batch address spaces. An attachment facility allows application programs to access DB2.

attribute. A characteristic of an entity. For example, in database design, the phone number of an employee is one of that employee's attributes.

authorization ID. A string that can be verified for connection to DB2 and to which a set of privileges are allowed. It can represent an individual, an organizational group, or a function, but DB2 does not determine this representation.

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Letra B

base table. A table created by the SQL CREATE TABLE statement that is used to hold persistent data. Contrast with result table and temporary table.

basic predicate. A predicate that compares two values.

binary integer. A basic data type that can be further classified as small integer or large integer.

bind. The process by which the output from the DB2 precompiler is converted to a usable control structure called a package or an application plan. During the process, access paths to the data are selected and some authorization checking is performed.

bit data. Data that is not associated with a coded character set.

BMP. Batch Message Processing (IMS).

bootstrap data set (BSDS). A VSAM data set tha contains name and status information for DB2, as well as RBA range specifications, for all active and archive log data sets. It also contains passwords for the DB2 directory and catalog, and lists of conditional restart and checkpoint records.

BSDS. Bootstrap data set.

buffer pool. Main storage reserved to satisfy the buffering requirements for one or more table spaces or indexes.

built-in function. Scalar function or column function.

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Letra C

cache structure. A coupling facilitystructure that stores data that can be available to all members of a Sysplex. A DB2 data sharing group uses cache structures as group buffer pools.

call level interface (CLI). A callable application program interface (API) for database access, which is an alternative to using embedded SQL. In contrast to embedded SQL, DB2 CLI does not require the user to precompile or bind applications, but instead provides a standard set of functions to process SQL statements and related services at run time.

cascade delete. The enforcement of referential constraints by DB2 when it deletes all descendent rows of a deleted parent row.

CASE expression. Allows an expression to be selected based on the evaluation of one or more conditions.

castout. The DB2 process of writing changed pages from a group buffer pool to DASD.

catalog. In DB2, a collection of tables that contains descriptions of objects such as tables, views, and indexes.

catalog table. Any table in the DB2 catalog.

CCSID. Coded character set identifier.

CDB. See communications database.

CDRA. Character data representation architecture.

character data representation architecture (CDRA). An architecture used to achieve consistent representation, processing, and interchange of string data.

character set. A defined set of characters.

check clause. An extension to the SQL CREATE TABLE and SQL ALTER TABLE statements that specifies a table check constraint.

check constraint. See table check constraint.

check integrity. The condition that exists when each row in a table conforms to the table check constraints defined on that table. Maintaining check integrity requires enforcing table check constraints on operations that add or change data.

check pending. A state of a table space or partition that prevents its use by some utilities and some SQL statements, because it can contain rows that violate referential constraints, table check constraints, or both.

checkpoint. A point at which DB2 records internal status information on the DB2 log that would be used in the recovery process if DB2 should abend.

CICS. Represents (in this publication) CICS/MVS and CICS/ESA.

CICS attachment facility. A DB2 subcomponent that uses the MVS Subsystem Interface (SSI) and cross storage linkage to process requests from CICS to DB2 and to coordinate resource commitment.

clause. In SQL, a distinct part of a statement, such as a SELECT clause or a WHERE clause.

CLI. See call level interface.

client. See requester.

clustering index. An index that determines how rows are physically ordered in a table space.

coded character set. A set of unambiguous rules that establish a character set and the one-to-one relationships between the characters of the set and their coded representations.

coded character set identifier (CCSID). A 16-bit number that uniquely identifies a coded representation of graphic characters. It designates an encoding scheme identifier and one or more pairs consisting of a character set identifier and an associated code page identifier.

code page. A set of assignments of characters to code points.

code point. In CDRA, a unique bit pattern that represents a character in a code page.

collection. A group of packages that have the same qualifier.

column. The vertical component of a table. A column has a name and a particular data type (for example, character, decimal, or integer).

column function. An SQL operation that derives its result from a collection of values across one or more rows. Contrast with scalar function.

"come from" checking. An LU 6.2 security option which defines a list of authorization IDs that are allowed to connect to DB2 from a partner LU.

command. A DB2 operator command or a DSN subcommand. Distinct from an SQL statement.

commit. The operation that ends a unit of work by releasing locks so that the database changes made by that unit of work can be perceived by other processes.

commit point. A point in time when data is considered consistent.

committed phase. The second phase of the multi-site update process that requests all participants to commit the effects of the logical unit of work.

communications database (CDB). A set of tables in the DB2 catalog that are used to establish conversations with remote database management systems.

comparison operator. A token (such as =, >, <) used to specify a relationship between two values.

composite key. An ordered set of key columns of the same table.

concurrency. The shared use of resources by more than one application process at the same time.

connection. The existence of a communication path between two partner LUs that allows information to be exchanged (for example, two DB2s connected and communicating by way of a conversation).

consistency token. A timestamp used to generate the version identifier for an application. See also version.

constant. A language element that specifies an unchanging value. Constants are classified as string constants or numeric constants. Contrast with variable.

constraint. A rule that limits the values that can be inserted, deleted, or updated in a table. See referential constraint, uniqueness constraint, and table check constraint.

conversation. (1) A VTAM term for a dialog between two application processes, on different DB2 subsystems, that is specified by a particular session name, mode name, and LU name. (2) An LU 6.2 security option which allows DB2 to require the user's authorization ID and password when allocating a conversation to a partner DB2. The user is validated by the partner DB2.

correlated subquery. A subquery (part of a WHERE or HAVING clause) applied to a row or group of rows of a table or view named in an outer sub-SELECT statement.

correlation ID. An identifier associated with a specific thread. In TSO, it is either an authorization ID or the job name.

correlation name. An identifier that designates a table, a view, or individual rows of a table or view within a single SQL statement. It can be defined in any FROM clause or in the first clause of an UPDATE or DELETE statement.

current data. Data within a host structure that is current with (identical to) the data within the base table.

cursor. A named control structure used by an application program to point to a row of interest within some set of rows, and to retrieve rows from the set, possibly making updates or deletions.

cursor stability (CS). The isolation level that provides maximum concurrency without the ability to read uncommitted data. With cursor stability, a unit of work holds locks only on its uncommitted changes and on the current row of each of its cursors.

cycle. A set of tables that can be ordered so that each table is a descendent of the one before it, and the first is a descendent of the last. A self-referencing table is a cycle with a single member.

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Letra D

DASD. Direct access storage device.

. database. A collection of tables, or a collection of table spaces and index spaces.

database access thread. A thread accessing data at the local subsystem on behalf of a remote subsystem.

database administrator (DBA). An individual responsible for the design, development, operation, safeguarding, maintenance, and use of a database.

database descriptor (DBD). An internal representation of DB2 database definition which reflects the data definition found in the DB2 catalog. The objects defined in a database descriptor are table spaces, tables, indexes, index spaces, and relationships.

database management system (DBMS). A software system that controls the creation, organization, and modification of a database and access to the data stored within it.

database request module (DBRM). A data set member created by the DB2 precompiler that contains information about SQL statements. DBRMs are used in the bind process.

DATABASE 2 Interactive (DB2I). The DB2 facility that provides for the execution of SQL statements, DB2 (operator) commands, programmer commands, and utility invocation.

data currency. The state in which data retrieved into a host variable in your program is a copy of data in the base table.

data sharing. The ability of two or more DB2 subsystems to directly access and change a single set of data.

data sharing group. A collection of one or more DB2 subsystems that directly access and change the same data while maintaining data integrity.

data sharing member. A DB2 subsystem assigned by XCF services to a data sharing group.

data type. An attribute of columns, literals, host variables, special registers, and the results of functions and expressions.

date. A three-part value that designates a day, month, and year.

date duration. A decimal integer that represents a number of years, months, and days.

datetime value. A value of the data type DATE, TIME, or TIMESTAMP.

DBA. Database administrator.

DBCS. Double-byte character set.

DBD. Database descriptor.

DBID. Database identifier.

DBMS. Database management system.

DBRM. Database request module.

DB2 catalog. Tables maintained by DB2 that contain descriptions of DB2 objects such as tables, views, and indexes.

DB2 command. An instruction to the DB2 subsystem allowing a user to start or stop DB2, to display information on current users, to start or stop databases, to display information on the status of databases, and so on.

DB2I. DATABASE 2 Interactive.

DB2 private protocol access. A method of accessing distributed data by which you can direct a query to another DB2 system by using an alias or a three-part name to identify the DB2 subsystems at which the statements are executed. Contrast with DRDA access.

DB2 private protocol connection. A DB2 private connection of the application process. See also private connection.

DCLGEN. Declarations generator.

DDF. Distributed data facility.

declarations generator (DCLGEN). A subcomponent of DB2 that generates SQL table declarations and COBOL, C, or PL/I data structure declarations that conform to the table. The declarations are generated from DB2 system catalog information. DCLGEN is also a DSN subcommand.

default value. A predetermined value, attribute, or option that is assumed when no other is explicitly specified.

deferred embedded SQL. SQL statements that are neither fully static nor fully dynamic. Like static statements, they are embedded within an application, but like dynamic statements, they are prepared during the execution of the application.

delete-connected. A table is delete-connected to table P if it is a dependent of P or a dependent of a table to which delete operations from P cascade.

delete rule. The rule that tells DB2 what to do to a dependent row when a parent row is deleted. For each relationship, the rule might be CASCADE, RESTRICT, SET NULL, or NO ACTION.

delimited identifier. A sequence of characters enclosed within quotation marks ("). The sequence must consist of a letter followed by zero or more characters, each of which is a letter, digit, or the underscore character (_).

delimiter token. A string constant, a delimited identifier, an operator symbol, or any of the special characters shown in syntax diagrams.

dependent. An object (row, table, or table space) is a dependent if it has at least one parent. The object is also said to be a dependent (row, table, or table space) of its parent. See parent row, parent table, parent table space.

dependent row. A row that contains a foreign key that matches the value of a primary key in the parent row.

dependent table. A table that is dependent in at least one referential constraint.

descendent. An object is a descendent of another object if it is a dependent of the object, or if it is the dependent of a descendent of that object.

descendent row. A row that is dependent on another row or a row that is a dependent of a descendent row.

descendent table. A table that is a dependent of another table or a dependent of a descendent table.

direct access storage device (DASD). A device in which access time is independent of the location of the data.

directory. The system database that contains internal objects such as database descriptors and skeleton cursor tables.

distributed data facility (DDF). A set of DB2 components through which DB2 communicates with another RDBMS.

distributed relational database architecture (DRDA). A connection protocol for distributed relational database processing that is used by IBM's relational database products. DRDA includes protocols for communication between an application and a remote relational database management system, and for communication between relational database management systems.

domain name. The name used by TCP/IP applications to refer to a TCP/IP host within a TCP/IP network.

domain name server (DNS). A special TCP/IP network server that manages a distributed directory that is used to map TCP/IP host names to IP addresses.

double-byte character set (DBCS). A set of characters used by national languages such as Japanese and Chinese that have more symbols than can be represented by a single byte. Each character is two bytes in length, and therefore requires special hardware to be displayed or printed.

double-precision floating point number. A 64-bit approximate representation of a real number.

DRDA. Distributed relational database architecture.

DRDA access. A method of accessing distributed data by which you can explicitly connect to another location, using an SQL statement, to execute packages that have been previously bound at that location. The SQL CONNECT statement is used to identify application servers, and SQL statements are executed using packages that were previously bound at those servers. Contrast with DB2 private protocol access.

DSN. (1) The default DB2 subsystem name. (2) The name of the TSO command processor of DB2. (3) The first three characters of DB2 module and macro names.

duration. A number that represents an interval of time. See date duration, labeled duration, and time duration.

dynamic SQL. SQL statements that are prepared and executed within an application program while the program is executing. In dynamic SQL, the SQL source is contained in host language variables rather than being coded into the application program. The SQL statement can change several times during the application program's execution.

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Letra E

EBCDIC. Extended binary coded decimal interchange code. An encoding scheme used to represent character data in the MVS, VM, VSE, and OS/400 environments. Contrast with ASCII.

EDM pool. A pool of main storage used for database descriptors and application plans.

embedded SQL. SQL statements coded within an application program. See static SQL.

encoding scheme. A set of rules to represent character data (ASCII or EBCDIC).

equi-join. A join operation in which the join-condition has the form expression = expression.

escape character. The symbol used to enclose an SQL delimited identifier. The escape character is the quotation mark ("), except in COBOL applications, where the symbol (either a quotation mark or an apostrophe) can be assigned by the user.

EUR. IBM European Standards.

exclusive lock. A lock that prevents concurrently executing application processes from reading or changing data. Contrast with shared lock.

executable statement. An SQL statement that can be embedded in an application program, dynamically prepared and executed, or issued interactively.

exit routine. A user-written (or IBM-provided default) program that receives control from DB2 to perform specific functions. Exit routines run as extensions of DB2.

exposed name. Names specified in a FROM clause are exposed or non-exposed. An exposed name is a correlation name or a table or view name for which a correlation name is not specified.

expression. An operand or a collection of operators and operands that yields a single value.

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Letra F

failed member state. A state of a member of a data sharing group. Failed member has permanent status recording with XCF, and its task, address space, or MVS system has terminated before the state changed from active to quiesced.

fallback. The process of returning to a previous release of DB2 after attempting or completing migration to a current release.

field procedure. A user-written exit routine designed to receive a single value and transform (encode or decode) it in any way the user can specify.

fixed-length string. A character or graphic string whose length is specified and cannot be changed. Contrast with varying-length string.

foreign key. A key that is specified in the definition of a referential constraint. Because of the foreign key, the table is a dependent table. The key must have the same number of columns, with the same descriptions, as the primary key of the parent table.

free space. The total unused space in a page, that is, the space not used to store records or control information.

full outer join. The result of a join operation that includes the matched rows of both tables being joined and preserves the unmatched rows of both tables. See also join.

function. A scalar function or column function. Same as built-in function.

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Letra G

GB. Gigabyte (1,073,741,824 bytes).

GBP-dependent. A page set or page set partition status when it is dependent upon the group bufferpool. There is either inter-DB2 read/write interest active for this page set or the page set has changed pages in the group buffer pool that have not yet been castout to DASD.

graphic string. A sequence of DBCS characters.

gross lock. The shared, update, or exclusive mode locks on a table, partition, or table space.

group buffer pool. A coupling facility cache structure used by a data sharing group to cache data and to ensure that the data is consistent for all members.

group name. The MVS XCF identifier for a data sharing group.

group restart. A restart of at least one member of a data sharing group after either locks or the shared communications area have been lost.

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Letra H

host. The set of programs and resources that are available on a given TCP/IP instance.

host identifier. A name declared in the host program.

host language. A programming language in which you can embed SQL statements.

host program. An application program written in a host language that contains embedded SQL statements.

host structure. In an application program, a structure referenced by embedded SQL statements.

host variable. In an application program, an application variable referenced by embedded SQL statements.

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Letra I

ICF. Integrated catalog facility.

image copy. An exact reproduction of all or part of a table space. DB2 provides utility programs to make full image copies (to copy the entire table space) or incremental image copies (to copy only those pages that have been modified since the last image copy).

IMS. Information Management System.

independent. An object (row, table, or table space) is independent if it is neither a parent nor a dependent of another object.

index. A set of pointers that are logically ordered by the values of a key. Indexes can provide faster access to data and can enforce uniqueness on the rows in a table.

index key. The set of columns in a table used to determine the order of index entries.

index partition. A VSAM data set that is contained within a partitioned index space.

index space. A page set used to store the entries of one index.

indicator variable. A variable used to represent the null value in an application program. If the value for the selected column is null, a negative value is placed in the indicator variable.

indoubt. A status of a unit of recovery. If DB2 fails after it has finished its phase 1 commit processing and before it has started phase 2, only the commit coordinator knows if this unit of recovery is to be committed or rolled back. At emergency restart, if DB2 does not have the information needed to make this decision, its unit of recovery is indoubt until DB2 obtains this information from the coordinator.

indoubt resolution. The process of resolving the status of an indoubt logical unit of work to either the committed or the rollback state.

inner join. The result of a join operation that includes only the matched rows of both tables being joined. See also join.

internal resource lock manager (IRLM). An MVS subsystem used by DB2 to control communication and database locking.

inter-DB2 R/W interest. A property of data in a table space, index, or partition that has been opened by more than one member of a data sharing group and that has been opened for writing by at least one of those members.

IP address. A 4-byte value that uniquely identifies a TCP/IP host.

IRLM. internal resource lock manager.

ISO. International Standards Organization.

isolation level. The degree to which a unit of work is isolated from the updating operations of other units of work. See also cursor stability, repeatable read, uncommitted read, and read stability.
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Letra J

JIS. Japanese Industrial Standard.

join. A relational operation that allows retrieval of data from two or more tables based on matching column values. See also full outer join, inner join, left outer join, outer join, right outer join, equi-join.

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Letra K

KB. Kilobyte (1024 bytes).

key. A column or an ordered collection of columns identified in the description of a table, index, or referential constraint.

keyword. In SQL, a name that identifies an option used in an SQL statement.

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Letra L

labeled duration. A number that represents a duration of years, months, days, hours, minutes, seconds, or microseconds.

large partitioned table space. A table space that allows the partitioned table it contains to exceed 64 GB of data in either compressed or uncompressed format.

leaf page. A page that contains pairs of keys and RIDs and that points to actual data. Contrast with nonleaf page.

left outer join. The result of a join operation that includes the matched rows of both tables being joined, and preserves the unmatched rows of the first table. See also join.

L-lock. See logical lock.

local. Refers to any object maintained by the local DB2 subsystem. local table, for example, is a table maintained by the local DB2 subsystem. Contrast with remote.

local subsystem. The unique RDBMS to which the user or application program is directly connected (in the case of DB2, by one of the DB2 attachment facilities).

location name. The name by which DB2 refers to a particular DB2 subsystem in a network of subsystems. Contrast with LU name.

lock. A means of controlling concurrent events or access to data. DB2 locking is performed by the IRLM.

lock duration. The interval over which a DB2 lock is held.

lock escalation. The promotion of a lock from a row or page lock to a table space lock because the number of page locks concurrently held on a given resource exceeds a preset limit.

locking. The process by which the integrity of data is ensured. Locking prevents concurrent users from accessing inconsistent data.

lock mode. A representation for the type of access concurrently running programs can have to a resource held by a DB2 lock.

lock object. The resource that is controlled by a DB2 lock.

lock promotion. The process of changing the size or mode of a DB2 lock to a higher level.

lock size. The amount of data controlled by a DB2 lock on table data; the value can be a row, a page, a table, or a table space.

log. A collection of records that describe the events that occur during DB2 execution and their sequence. The information thus recorded is used for recovery in the event of a failure during DB2 execution.

logical index partition. The set of all keys that reference the same data partition.

logical lock. The lock type used by transactions to control intra- and inter-DB2 data concurrency between transactions.

logical unit. An access point through which an application program accesses the SNA network in order to communicate with another application program.

logical unit of work (LUW). In IMS, the processing that program performs between synchronization points.

log initialization. The first phase of restart processing during which DB2 attempts to locate the current end of the log.

log record sequence number (LRSN). A number DB2 generates and associates with each log record. DB2 also uses the LRSN for page versioning. The LRSNs generated by a given DB2 data sharing group form a strictly increasing sequence for each DB2 log and a strictly increasing sequence for each page across the DB2 group.

log truncation. A process by which an explicit starting RBA is established. This RBA is the point at which the next byte of log data will be written.

long string. A string whose actual length, or a varying-length string whose maximum length, is greater than 255 bytes or 127 double-byte characters.

LRSN. See log record sequence number.

LU name. From logical unit ame, the name by which VTAM refers to a node in a network. Contrast with location name.

LUW. Logical unit of work.

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Letra M

member name. The MVS XCF identifier for a particular DB2 subsystem in a data sharing group.

migration. The process of converting a DB2 subsystem with a previous release of DB2 to an updated or current release. In this process, you can acquire the functions of the updated or current release without losing the data you created on the previous release.

mixed data string. A character string that can contain both single-byte and double-byte characters.

mode name. A VTAM name for the collection of physical and logical characteristics and attributes of a session.

multi-site update. Distributed relational database processing in which data is updated in more than one location within a single unit of work.

MVS. Multiple Virtual Storage.

MVS/ESA. Multiple Virtual Storage/Enterprise Systems Architecture.

MVS/XA. Multiple Virtual Storage/Extended Architecture.

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Letra N

nested table expression. A subselect in a FROM clause (surrounded by parentheses).

nonleaf page. A page that contains keys and page numbers of other pages in the index (either leaf or nonleaf pages). Nonleaf pages never point to actual data.

nonpartitioned index. Any index that is not a partitioned index.

NUL. In C, a single character that denotes the end of the string.

null. A special value that indicates the absence of information.

NULLIF. A scalar function which evaluates two passed expressions, returning NULL if the arguments are equal, or the value of the first argument if they are not.

NUL-terminated host variable. A varying-length host variable in which the end of the data is indicated by the presence of a NUL terminator.

NUL terminator. In C, the value that indicates the end of a string. For character strings, the NUL terminator is X'00'.

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Letra O

OBID. Data object identifier.

ordinary identifier. An uppercase letter followed by zero or more characters, each of which is an uppercase letter, a digit, or the underscore character. An ordinary identifier must not be a reserved word.

ordinary token. A numeric constant, an ordinary identifier, a host identifier, or a keyword.

outer join. The result of a join operation that includes the matched rows of both tables being joined and preserves some or all of the unmatched rows of the tables being joined. See also join.

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Letra P

package. Also application package. An object containing a set of SQL statements that have been bound statically and that are available for processing.

package list. An ordered list of package names that may be used to extend an application plan.

package name. The name given an object created by a BIND PACKAGE or REBIND PACKAGE command. The object is a bound version of a database request module (DBRM). The name consists of a location name, a collection ID, a package ID, and a version ID.

page. A unit of storage within a table space (4KB or 32KB) or index space (4KB). In a table space, a page contains one or more rows of a table.

page set. A table space or index space consisting of pages that are either 4KB or 32KB in size. Each page set is made from a collection of VSAM data sets.

parallel I/O processing. A form of I/O processing in which DB2 initiates multiple concurrent requests for a single user query and performs I/O processing concurrently (in parallel), on multiple data partitions.

parameter marker. A question mark (?) that appears in a statement string of a dynamic SQL statement. The question mark can appear where a host variable could appear if the statement string was a static SQL statement.

parent key. A primary key or unique key in the parent table of a referential constraint. The values of a parent key determine the valid values of the foreign key in the referential constraint.

parent row. A row whose primary key value is the foreign key value of a dependent row.

parent table. A table whose primary key is referenced by the foreign key of a dependent table.

parent table space. A table space that contains a parent table. A table space containing a dependent of that table is a dependent table space.

partition. A portion of a page set. Each partition corresponds to a single, independently extendable data set. Partitions can be extended to a maximum size of 1, 2, or 4 gigabytes, depending upon the number of partitions in the partitioned page set. All partitions of a given page set have the same maximum size.

partitioned data set (PDS). A data set in direct access storage that is divided into partitions, called members, each of which can contain a program, part of a program, or data. Synonymous with program library.

partitioned table space. A table space subdivided into parts (based upon index key range), each of which may be processed by utilities independently.

PDS. Partitioned data set.

piece. A data set of a nonpartitioned page set.

plan. See application plan.

plan allocation. The process of allocating DB2 resources to a plan in preparation to execute it.

plan name. The name of an application plan.

point of consistency. A time when all recoverable data an application accesses is consistent with other data. Synonymous with sync point or commit point. precompilation. A processing of application programs containing SQL statements that takes place before compilation. SQL statements are replaced with statements that are recognized by the host language compiler. Output from this precompilation includes source code that can be submitted to the compiler and the database request module (DBRM) that is input to the bind process.

predicate. An element of a search condition that expresses or implies a comparison operation.

prefix. A code at the beginning of a message or record.

prepare. The first phase of a two-phase commit process in which all participants are requested to prepare for commit.

prepared SQL statement. A named object that is the executable form of an SQL statement that has been processed by the PREPARE statement.

primary authorization ID. The authorization ID used to identify the application process to DB2.

primary index. An index that enforces the uniqueness of a primary key.

primary key. A unique, nonnull key that is part of the definition of a table. A table cannot be defined as a parent unless it has a unique key or primary key.

private connection. A communications connection that is specific to DB2.

privilege. The capability of performing a specific function, sometimes on a specific object. The term includes: privilege set. For the installation SYSADM ID, the set of all possible privileges. For any other authorization ID, the set of all privileges recorded for that ID in the DB2 catalog.

process. A general term for a unit that depends on the environment, but has the same basic properties in every environment. A process involves the execution of one or more programs, and is the unit to which resources and locks are allocated. The execution of an SQL statement is always associated with some process.

program. A single compilable collection of executable statements in a programming language.

protected conversation. A VTAM conversation that supports two-phase commit flows.

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Letra Q

QMF. Query Management Facility.

query. A component of certain SQL statements that specifies a result table.

quiesced member state. A state of a member of a data sharing group. An active member becomes quiesced when a STOP DB2 command takes effect without a failure. If the member's task, address space, or MVS system fails before the command takes effect, the member state is failed.

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Letra R

RACF. OS/VS2 MVS Resource Access Control Facility.

RDB. See relational database.

RDBMS. Relational database management system.

RDBNAM. See relational database name.

read stability (RS). An isolation level that is similar to repeatable read but does not completely isolate an application process from all other concurrently executing application processes. Under level RS, an application that issues the same query more than once might read additional rows, known as phantom rows, that were inserted and committed by a concurrently executing application process.

rebind. To create a new application plan for an application program that has been bound previously. If, for example, you have added an index for a table accessed by your application, you must rebind the application in order to take advantage of that index.

record. The storage representation of a row or other data.

recovery. The process of rebuilding databases after a system failure.

recovery log. A collection of records that describes the events that occurs during DB2 execution and their sequence. The information recorded is used for recovery in the event of a failure during DB2 execution.

referential constraint. The requirement that nonnull values of a designated foreign key are valid only if they equal values of the primary key of a designated table.

referential integrity. The condition that exists when all intended references from data in one column of a table to data in another column of the same or a different table are valid. Maintaining referential integrity requires enforcing referential constraints on all LOAD, RECOVER, INSERT, UPDATE, and DELETE operations.

referential structure. A set of tables and relationships that includes at least one table and, for every table in the set, all the relationships in which that table participates and all the tables to which it is related.

relational database. A database that can be perceived as a set of tables and manipulated in accordance with the relational model of data.

relational database management system (RDBMS). A relational database manager that operates consistently across supported IBM systems.

relational database name (RDBNAM). A unique identifier for an RDBMS within a network. In DB2, this must be the value in the LOCATION column of table SYSIBM.LOCATIONS in the CDB. DB2 publications refer to the name of another RDBMS as a LOCATION value or a location name.

relationship. A defined connection between the rows of a table or the rows of two tables. A relationship is the internal representation of a referential constraint.

remote. Refers to any object maintained by a remote DB2 subsystem; that is, by a DB2 subsystem other than the local one. A remote view, for instance, is a view maintained by a remote DB2 subsystem. Contrast with local.

remote subsystem. Any RDBMS, except the local subsystem, with which the user or application can communicate. The subsystem need not be remote in any physical sense, and may even operate on the same processor under the same MVS system.

repeatable read (RR). The isolation level that provides maximum protection from other executing application programs. When an application program executes with repeatable read protection, rows referenced by the program cannot be changed by other programs until the program reaches a commit point.

request commit. The vote submitted to the prepare phase if the participant has modified data and is prepared to commit or roll back.

requester. Also application requester (AR). The source of a request to a remote RDBMS, the system that requests the data.

resource. The object of a lock or claim, which could be a table space, an index space, a data partition, an index partition, or a logical partition.

resource limit facility (RLF). A portion of DB2 code that prevents dynamic manipulative SQL statements from exceeding specified time limits.

result set. The set of rows returned to a client application by a stored procedure.

result set locator. A 4-byte value used by DB2 to uniquely identify a query result set returned by a stored procedure.

result able. The set of rows specified by a SELECT statement.

right outer join. The result of a join operation that includes the matched rows of both tables being joined and preserves the unmatched rows of the second join operand. See also join. RLF. Resource limit facility.

rollback. The process of restoring data changed by SQL statements to the state at its last commit point. All locks are freed. Contrast with commit.

row. The horizontal component of a table. A row consists of a sequence of values, one for each column of the table.

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Letra S

SBCS. Single-byte character set.

scalar function. An SQL operation that produces a single value from another value and is expressed as a function name followed by a list of arguments enclosed in parentheses. See also column function.

search condition. A criterion for selecting rows from a table. A search condition consists of one or more predicates.

secondary authorization ID. An authorization ID that has been associated with a primary authorization ID by an authorization exit routine.

segmented table space. A table space that is divided into equal-sized groups of pages called segments. Segments are assigned to tables so that rows of different tables are never stored in the same segment.

self-referencing constraint. A referential constraint that defines a relationship in which a table is a dependent of itself.

self-referencing table. A table with a self-referencing constraint.

sequential prefetch. A mechanism that triggers consecutive asynchronous I/O operations. Pages are fetched before they are required, and several pages are read with a single I/O operation.

server. Also application server (AS). The target for a request from a remote RDBMS, the RDBMS that provides the data.

shared lock. A lock that prevents concurrently executing application processes from changing data, but not from reading data.

shift-in character. A special control character (X'0F') used in EBCDIC systems to denote that the following bytes represent SBCS characters. See shift-out character.

shift-out character. A special control character (X'0E') used in EBCDIC systems to denote that the following bytes, up to the next shift-in control character, represent DBCS characters.

short string. A string whose actual length, or a varying-length string whose maximum length, is 255 bytes (127 double-byte characters) or less.

sign-on. A request made on behalf of an individual CICS or IMS application process by an attach facility to enable DB2 to verify that it is authorized to use DB2 resources.

simple table space. A table space that is neither partitioned nor segmented.

single-byte character set (SBCS). A set of characters in which each character is represented by a single byte.

single-precision floating point number. A 32-bit approximate representation of a real number.

SMF. System management facility.

SMS. Storage Management Subsystem.

socket. A callable TCP/IP programming interface that is used by TCP/IP network applications to communicate with remote TCP/IP partners.

source program. A set of host language statements and SQL statements that is processed by an SQL precompiler.

space. A sequence of one or more blank characters.

special register. A storage area that is defined for a process by DB2 and is used to store information that can be referenced in SQL statements. Examples of special registers are USER, CURRENT DATE, and CURRENT TIME.

SPUFI. SQL Processor Using File Input. A facility of the TSO attachment subcomponent that enables the DB2I user to execute SQL statements without embedding them in an application program.

SQL. Structured Query Language.

SQL authorization ID (SQL ID). The authorization ID that is used for checking dynamic SQL statements in some situations.

SQL communication area (SQLCA). A structure used to provide an application program with information about the execution of its SQL statements.

SQL descriptor area (SQLDA). A structure that describes input variables, output variables, or the columns of a result table.

SQL escape character. The symbol used to enclose an SQL delimited identifier. This symbol is the quotation mark ("). See escape character.

SQL ID. SQL authorization ID.

SQL return code. Either SQLCODE or SQLSTATE.

SQL string delimiter. A symbol used to enclose an SQL string constant. The SQL string delimiter is the apostrophe ('), except in COBOL applications, in which case the symbol (either an apostrophe or a quotation mark) may be assigned by the user.

SQLCA. SQL communication area.

SQLDA. SQL descriptor area.

SQL/DS. SQL/Data System. Also known as DB2/VSE & VM.

SSI. MVS subsystem interface.

static SQL. SQL statements, embedded within a program, that are prepared during the program preparation process (before the program is executed). After being prepared, the SQL statement does not change (although values of host variables specified by the statement might change).

storage group. A named set of DASD volumes on which DB2 data can be stored.

stored procedure. A user-written application program, that can be invoked through the use of the SQL CALL statement.

string. See character string or graphic string.

Structured Query Language (SQL). A standardized language for defining and manipulating data in a relational database.

subpage. The unit into which a physical index page can be divided.

subquery. A SELECT statement within the WHERE or HAVING clause of another SQL statement; a nested SQL statement.

subselect. That form of a query that does not include ORDER BY clause, UPDATE clause, or UNION operators.

substitution character. A unique character that is substituted during character conversion for any characters in the source program that do not have a match in the target coding representation.

subsystem. A distinct instance of a RDBMS.

sync point. See commit point.

synonym. In SQL, an alternative name for a table or view. Synonyms can only be used to refer to objects at the subsystem in which the synonym is defined.

system administrator. The person having the second highest level of authority within DB2. System administrators make decisions about how DB2 is to be used and implement those decisions by choosing system parameters. They monitor the system and change its characteristics to meet changing requirements and new data processing goals.

system conversation. The conversation that two DB2s must establish to process system messages before any distributed processing can begin.

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Letra T

table. A named data object consisting of a specific number of columns and some number of unordered rows. Synonymous with base table or temporary table.

table check constraint. A user-defined constraint that specifies the values that specific columns of a base table can contain.

table space. A page set used to store the records in one or more tables.

TCP/IP. A network communication protocol used by computer systems to exchange information across telecommunication links.

TCP/IP port. A 2-byte value that identifies an end user or a TCP/IP network application within a TCP/IP host.

temporary table. A table created by the SQL CREATE GLOBAL TEMPORARY TABLE statement that is used to hold temporary data. Contrast with result table and temporary table.

thread. The DB2 structure that describes an application's connection, traces its progress, processes resource functions, and delimits its accessibility to DB2 resources and services. Most DB2 functions execute under a thread structure. See also allied thread and database access thread.

three-part name. The full name of a table, view, or alias. It consists of a location name, authorization ID, and an object name separated by a period.

time. A three-part value that designates a time of day in hours, minutes, and seconds.

time duration. A decimal integer that represents a number of hours, minutes, and seconds.

time-sharing option (TSO). Provides interactive time sharing from remote terminals.

timestamp. A seven-part value that consists of a date and time expressed in years, months, days, hours, minutes, seconds, and microseconds.

trace. A DB2 facility that provides the ability to monitor and collect DB2 monitoring, auditing, performance, accounting, statistics, and serviceability (global) data.

transaction program name. In SNA LU 6.2 conversations, the name of the program at the remote logical unit that will be the other half of the conversation.

TSO. Time-sharing option.

type 1 indexes. Indexes that were created by a release of DB2 before DB2 Version 4 or that are specified as type 1 indexes in Version 4. Contrast with type 2 indexes.

type 2 indexes. A new type of indexes available in Version 4. They differ from type 1 indexes in several respects; for example, they are the only indexes allowed on a table space that uses row locks.

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Letra U

uncommitted read (UR). The isolation level that allows an application to read uncommitted data.

underlying view. The view upon which another view is directly or indirectly defined.

UNION. An SQL operation that combines the results of two select statements. UNION is often used to merge lists of values obtained from several tables.

unique index. An index which ensures that no identical key values are stored in a table.

uniqueness constraint. The rule that no two values in a primary key or key of a unique index can be the same.

unit of recovery. A recoverable sequence of operations within a single resource manager, such as an instance of DB2. Contrast with unit of work.

unit of work. A recoverable sequence of operations within an application process. At any time, an application process is a single unit of work, but the life of an application process can involve many units of work as a result of commit or rollback operations. In a multi-site update operation, a single unit of work can include several units of recovery.

UT. Utility-only access.

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Letra V

value. The smallest unit of data manipulated in SQL.

variable. A data element that specifies a value that can be changed. A COBOL elementary data item is an example of a variable. Contrast with constant.

varying-length string. A character or graphic string whose length varies within set limits. Contrast with fixed-length string.

version. A member of a set of similar programs, DBRMs, or packages.



view. An alternative representation of data from one or more tables. A view can include all or some of the columns contained in tables on which it is defined.

view check option. An option that specifies whether every row that is inserted or updated through a view must conform to the definition of that view. A view check option can be specified with the WITH CASCADED CHECK OPTION, WITH CHECK OPTION, or WITH LOCAL CHECK OPTION clauses of CREATE VIEW.

Virtual Telecommunications Access Method (VTAM). An IBM licensed program that controls communication and the flow of data in an SNA network.

VSAM. Virtual storage access method.

VTAM. MVS Virtual telecommunication access method.

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