Glossary
- access method
- A set of server functions that Universal Server uses to access and manipulate an index or a table. See primary access method and secondary access method.
- access privilege
- An operation that a user has permission to perform in a specific database, table, table fragment, or column.
- active set
- The set of rows returned by a SELECT statement
- aggregate function
- A function that returns a single value by performing a mathematical operation on one or more rows, for example, sum, average, minimum, or maximum. Also called math functions or set functions.
- API
- Acronym for Application Programming Interface.
- application process
- The process that manages an ESQL/C program at runtime, executes the program logic, and initiates SQL requests. Memory that is allocated for program variables, program data, and the fetch buffer is part of the application process. See also database server process.
- application programming interface (API)
- A term used to refer to a library of related routines that provide access to a particular product or feature.
- application program
- An executable file or logically related set of files that perform one or more database management tasks.
- argument
- A value passed to a function, routine, stored procedure, or command.
- array
- An ordered set of items of the same data type. Individual members of the array are usually distinguished by an integer argument that gives the position of the element in the array.
- attached index
- An index that is created without a fragmentation strategy. An attached index can also be an index created on a fragmented table.
- auxiliary statements
- The SQL statements that you use to obtain auxiliary information about tables and databases. These statements include INFO, OUTPUT, WHENEVER, and GET DIAGNOSTICS.
- B-tree index
- A type of index that uses a balanced tree structure for efficient record retrieval. A B-tree index is balanced when the leaf nodes are all at the same level from the root node. B-tree indexes store key data in ascending or descending order.
- base type
- See opaque data type.
- blob
- Legacy term for simple large object.
- BLOB
- Binary Large Object. A smart large object that stores any type of binary data, including images. A BLOB can be stored and retrieved in pieces and has database properties such as recovery and transaction rollback.
- blobpage
- The unit of disk allocation within a blobspace. The size of a blobpage is determined by the DBA and can vary from blobspace to blobspace.
- blobspace
- A logical collection of chunks that is used to store TEXT and BYTE data.
- BOOLEAN
- A built-in data type that supports two one-byte values, one for a true condition and another for a false condition. External representation of these two values is `
t' and `f', respectively.
- Boolean function
- An external function or SPL function that returns only a Boolean value (TRUE or FALSE).
- built-in data type
- A fundamental data type defined by the database server, for example, INTEGER, CHAR, or SERIAL8.
- BYTE
- A data type for a simple large object that stores any type of binary data and can be as large as 231 bytes.
- cascading deletes
- A feature that causes the deletion of rows from a child table that were associated by foreign key to a row that is deleted from the parent table.
- cast
- A mechanism that the database server uses to convert data from one data type to another.
- casting function
- A function that is used to implement a cast. The function performs the necessary operations for conversion between two data types. The function must be registered as a cast with the CREATE CAST statement before it can be used.
- check constraint
- A condition that must be met before data can be assigned to a table column during an INSERT or UPDATE statement.checkpoint
- checkpoint
- A point in time during a database server operation when the pages on disk are synchronized with the pages in the shared memory buffer pool.
- chunk
- The largest contiguous section disk space available. A group of chunks defines a dbspace or blobspace.
- client
- An application program that requests services from a server program, typically a file server or a database server.
- client/server
architecture
- A hardware and software design that allows the user interface and database server to reside on separate nodes or platforms on a single computer or over a network.
- client/server connection statements
- The SQL statements that you use to make connections with databases. These statements include CONNECT, DISCONNECT, and SET CONNECTION.
- CLOB
- Character Large Object. A smart large object that stores large text items, such as PostScript or HTML files. A CLOB can be stored and retrieved in pieces and has database properties such as recovery and transaction rollback.
- cluster an index
- To rearrange the physical data of a table according to a specific index.
- cluster key
- The column in a table that logically relates a group of blobs stored in an optical cluster.
- clustersize
- The amount of space, specified in kilobytes, that is allocated to an optical cluster on an optical volume.
- collating sequence
- The sequence of values that specifies some logical order in which the character fields in a database are sorted and indexed. Collating sequence is also known as collation order.
- collection
- An instance of a collection data type; a group of elements of the same data type stored in a SET, MULTISET, or LIST.
- collection cursor
- A database cursor that has an INFORMIX-ESQL/C collection variable associated with it and provides access to the individual elements of a column whose data type is a collection data type.
- collection derived table
- A table that INFORMIX-ESQL/C or SPL creates for a collection column when it encounters the TABLE keyword in an INSERT, DELETE, UPDATE, or SELECT statement. ESQL/C and SPL store this table in a collection variable to access elements of the collection as rows of the collection derived table.
- collection data type
- A complex data type whose instances are groups of elements of the same data type, which can be any opaque data type, distinct data type, built-in data type, collection data type, or row type.
- collection variable
- An INFORMIX-ESQL/C host variable or SPL variable that holds an entire collection and provides access, through a collection cursor, to the individual elements of the collection.
- column
- A data element that contains a particular type of information that occurs in every row in the table. Also see row.
- column expression
- An expression that includes a column name and optionally uses column subscripts to define a column substring.
- COMMIT WORK
- A statement used to complete a transaction by accepting all changes to the database since the beginning of the transaction. See transaction, ROLLBACK WORK.
- complex data type
- A data type that is built from a combination of other data types using an SQL type constructor and whose components can be accessed through SQL statements. See row type, collection type, and reference type.
- composite index
- An index constructed on two or more columns of a table. The ordering imposed by the composite index varies least frequently on the first-named column and most frequently on the last-named column.
- composite data type
- See row type.
- concurrency
- The ability of two or more processes to access the same database simultaneously.
- connection
- An association between an application and a database environment, created by a CONNECT or DATABASE statement. Database servers can also have connections to one another. See also explicit connection and implicit connection.
- constant
- A nonvarying data element or value.
- constraint
- A restriction on what kinds of data can be inserted or updated in tables. See also check constraint, primary-key constraint, referential constraint, not null constraint, and unique constraint.
- constructed data type
- See complex data type.
- constructor
- See type constructor.
- correlated subquery
- A subquery (or inner SELECT) that depends on a value produced by the outer SELECT statement that contains it.
- correlation name
- The prefix that you can use with a column name in a triggered action to refer to an old (before triggering statement) or a new (after triggering statement) column value. The associated column name must belong to the triggering table.
- cursor
- An identifier associated with a group of rows or a collection data type and that points to one row or collection element at a time.
- cursor function
- A user-defined function that returns one or more rows of data and therefore requires a cursor to execute. An SPL function is a cursor function when its RETURN statement contains the WITH RESUME keywords. An external function is a cursor function when it is defined as an iterator function.
- data distribution
- A mapping of the data in a column into a set of the column values, in which the contents of the column are examined and divided into bins, each of which represents a percentage of the data. The organization of column values into bins is called the distribution for that column.
- data integrity
- The process of ensuring that data corruption does not occur when multiple users simultaneously try to alter the same data. Locking and transaction processing are used to control data integrity.
- data integrity statements
- The SQL statements that you use to control transactions and audits. Data integrity statements also include statements for repairing and recovering tables.
- data manipulation statements
- The SQL statements that you use to query tables, insert into tables, delete from tables, update tables, and load into and unload from tables.
- data replication
- The ability to allow database objects to have more than one representation at more than one distinct site.
- data restriction
- Synonym for constraint. See constraint.
- data type
- A descriptor assigned to a variable or column that indicates the type of data that the variable or column can hold. See built-in data type, user-defined data type, opaque data type, complex data type, distinct data type.
- database
- A collection of information (contained in tables) that is useful to a particular organization or used for a specific purpose.
- database administrator
- The individual responsible for the contents and use of a database.
- database application
- A program that applies database management techniques to implement specific data manipulation and reporting tasks.
- database environment
- Used in the CONNECT statement, either the database server or the database server and database to which a user connects.
- database
object
- In the broad sense, any SQL entity recorded in a system catalog table, such as a table, index, or SPL procedure.
- DataBlade API
- An API of C routines that a C-language external routine must use instead of SQL statements to access data in INFORMIX-Universal Server.
- DataBlade module
- A collection of related data types, routines, operators, and access methods that extend an object-relational database to manage new kinds of data or add new features.
- DBA
- Acronym for Database Administrator.
- DBMS
- Acronym for database management system. It is all the components necessary to create and maintain a database, including the application development tools and the database server.
- dbspace
- A logical collection of one or more chunks. Because chunks represent specific regions of disk space, the creators of databases and tables can control where their data is physically located by placing databases or tables in specific dbspaces.
- declaration statement
- A programming language statement that describes or defines objects, for example, defining a program variable. Compare to procedural statement.
- default value
- A value inserted into a column or variable when an explicit value is not specified. Default values can be assigned to columns using the ALTER TABLE and CREATE TABLE statements and to variables in stored procedures.
- detached index
- An index that is created with a fragmentation strategy or with the IN dbspace storage option.
- disabled mode
- The object mode in which a database object is disabled. When a constraint, index, or trigger is in the disabled mode, the database server acts as if the object does not exist and does not take it into consideration during the execution of data manipulation statements.
- distinct data type
- A data type that you create with the CREATE DISTINCT TYPE statement. A distinct data type has the same internal storage representation as its source type (an existing opaque data type, built-in data type, named row type, or distinct data type), but has a different name. To compare a distinct data type with its source type requires an explicit cast. A distinct data type inherits all routines that are defined on its source type.
- duplicate index
- An index that allows duplicate values in the indexed column.
- dynamic
routine-name specification
- The execution of a routine whose name is determined at runtime through an SPL variable, instead of the explicit name of a routine, in the EXECUTE PROCEDURE or EXECUTE FUNCTION statement.
- element
- A member of a collection. An element can be a single value of any built-in data type, opaque data type, distinct data type, named row type, unnamed row type, or collection data type.
- element type
- The data type of the elements in a collection.
- enabled mode
- The default object mode of database objects. When a constraint, index, or trigger is in this mode, the database server recognizes the existence of the object and takes the object into consideration while executing data manipulation statements. Also see object mode.
- end-user function
- See end-user routine.
- end-user routine
- A user-defined routine that end users can specify within an SQL statement to operate on a data type.
- ESQL/C Smart Large-Object API
- An API of C routines that an INFORMIX-ESQL/C client application can use to access smart large objects as operating-system files. The ESQL/C Smart Large-Object API is part of the INFORMIX-ESQL/C SQL API. Smart large objects can also be accessed by a set of functions in the DataBlade API.
- exclusive
access
- When a user has sole access to a database or table and other users are prevented from using it.
- exclusive
lock
- A lock on an object (row, page, table, or database) that is held by a single thread that prevents other processes from acquiring a lock of any kind on the same object.
- explicit cast
- A cast that requires a user to specify the CAST AS keyword or cast operator (::) to convert data from one data type to another
- explicit
connection
- A connection made to a database environment that uses the CONNECT statement.
- explicit select list
- A SELECT statement in which the user explicitly specifies the columns that the query returns.
- extended data type
- A term used to refer to data types that are not built-in; namely complex data types, opaque data types, and distinct data types.
- external function
- An external routine that can accept one or more arguments and returns a single value.
- external procedure
- An external routine that can accept one or more arguments, but does not return a value.
- external routine
- A routine written in a language external to the database (for example, C), whose body is stored outside the database, but whose name and parameters are registered in the system catalog tables.
- external space
- Storage space that is managed by a user-defined access method rather than the database server. You can specify the name of an external space, instead of the name of the name of a dbspace, in the IN clause of the CREATE TABLE and CREATE INDEX statements.
- field
- A component of a named row type or unnamed row type that contains a name and a data type and can be accessed in an SQL statement by using dot notation in the form row type name.field name.
- filter
- A set of conditions for selecting rows.
1) The conditional expression in the WHERE clause is a filter that controls the set of rows that a query evaluates. This filter is sometimes referred to as a predicate.
2) The High-Performance Loader (HPL) uses a filter component to load a subset of rows.
- foreign key
- A column, or set of columns, that references a unique or primary key in a table. For every entry in a foreign-key column, there must exist a matching entry in the unique or primary column, if all foreign-key columns contain non-null values.
- function
- A routine that can accept arguments and returns one or more values. See user-defined function.
- function cursor
- A cursor that is associated with an EXECUTE FUNCTION statement, which executes routines that return values. See cursor function.
- function overloading
- See routine overloading.
- gateway
- A data communications device that establishes communications between networks.
- global variable
- A variable whose value can be accessed from any ESQL/C or SPL routine in a program. Its scope is the entire program. Global variables should not be used in routines written with the DataBlade API.
- GLS
- See Global Language Support.
- GLS API
- An API of C routines that a C-language external routine can use to access Informix GLS locales. This API also includes functions that obtain culture-specific collation order, time and date formats, and numeric formats, and functions that provide a uniform way of accessing character data, regardless of whether the locale supports single-byte characters or multibyte characters.
- hash rule
- A user-defined algorithm that maps each row in a table to a set of hash values and that is used to determine the fragment in which a row is stored.
- host variable
- A C program variable that is referenced in an embedded statement. A host variable is identified by the dollar sign ( $ ) or colon ( : ) that precedes it.
- identifier
- A sequence of letters, digits, and underscores ( _ ) that represents the name of a database, table, column, cursor, function, index, synonym, alias, view, prepared object, constraint, or procedure name.
- implicit cast
- A cast that the database server automatically performs to convert data from one data type to another. See also explicit cast.
- implicit connection
- A connection made using a database statement (DATABASE, CREATE DATABASE, START DATABASE, DROP DATABASE). See also explicit connection.
- implicit select list
- A SELECT statement that uses the asterisk (*) symbol so that a query returns all columns of the table.
- index
- A structure of pointers that point to rows of data in a table. An index optimizes the performance of database queries by ordering rows to make access faster.
- index fragment
- Consists of zero or more index items grouped together, which can be stored in the same dbspace as the associated table fragment or, if you choose, in a separate dbspace.
- Informix user ID
- A login user ID (login user name) that must be valid on all computer systems (operating systems) involved in the client's database access. Often referred to as the client's user ID or user name.
- Informix user password
- A user ID password that must be valid on all computer systems (operating systems) involved in the client's database access. When the client specifies an explicit user ID, most computer systems require the Informix user password to validate the user ID.
- inheritance
- The process that allows an object to acquire the properties of another object. Inheritance allows for incremental modification, so that an object can inherit a general set of properties and add properties that are specific to itself. See type inheritance and table inheritance.
- input parameter
- A placeholder within a prepared SQL statement that indicates a value is to be provided at the time the statement is executed.
- insert cursor
- A cursor that is associated with an INSERT statement.
- installation
- The loading of software from some magnetic medium (tape, cartridge, or floppy disk) or CD onto a computer and preparing it for use.
- interquery parallelization
- The ability to process multiple queries simultaneously to avoid a performance delay when multiple independent queries access the same table. Also see intraquery parallelization.
- intraquery parallelization
- The ability to break a single query into subqueries and process the subqueries in parallel in order to reduce data retrieval time and improve performance. Also see interquery parallelization.
- isolation
- The level of independence among multiple users when they attempt to access common data, specifically relating to the locking strategy for read-only SQL requests. The various levels of isolation are distinguished primarily by the length of time that shared locks are (or can be) acquired and held.
- iterator function
- A cursor function that is an external function, written in an external programming language such as C.
- jagged rows
- A query result in which rows differ in the number and type of columns they contain, because the query applies to more than one table in a table hierarchy.
- key
- The pieces of information that are used to locate a row of data. A key defines the pieces of information you want to search for, as well as the order in which you want to process information in a table.
- keyword
- A word that has meaning to a program. For example, the word SELECT is a keyword in SQL.
- large object
- A data object that is logically stored in a table column but physically stored independently of the column, due to its size. Large objects can be simple large objects (TEXT, BYTE) or smart large objects (CLOB, BLOB).
- library
- A collection of precompiled functions or routines that are designed to perform tasks which are common to a particular kind of application.
- link
- The process of combining separately compiled program modules into an executable program.
- literal
- A character or numeric constant.
- LIST
- A collection data type created with the LIST constructor in which elements are ordered and duplicates are allowed.
- local variable
- A variable that has meaning only in the module in which it is defined. Its scope is the routine that defines it. See variable and scope of reference.
- lock coupling
- When an R-tree index is updated, lock coupling is used if a leaf's bounding box has changed. The change must be propagated to the parent node. The propagation is accomplished by moving upwards in the tree until a parent node that does not need to be changed is reached. Lock coupling is used during this upward movement. That is, a lock is held on the child node until a lock is obtained on the parent node.
- lock mode
- An option that describes whether a user who requests a lock on an already locked object is to not wait for the lock and instead receive an error, wait until the object is released to receive the lock, or wait a certain amount of time before receiving an error.
- locking
- The process of temporarily limiting access to an object (database, table, page, or row) to prevent conflicting interactions among concurrent processes.
- locking granularity
- The size of a locked object. The size may be a database, table, page, or row.
- LVARCHAR
- A built-in data type that stores varying-length character data of up to 32 kilobytes.
- math functions
- See aggregate functions.
- mirroring
- The process of storing the same data on two chunks simultaneously, so that if one chunk fails, the data is still usable on the other chunk.
- MULTISET
- A collection data type created with the MULTISET constructor in which elements are not ordered and duplicates are allowed.
- named row type
- A row type created with the CREATE ROW TYPE statement that has a defined name and inheritance properties and can be used to construct a typed table. A named row type is not equivalent to another named row type, even if its field definitions are the same.
- node
- In indexing of relational databases, an ordered group of key values having a fixed number of elements. A B+ tree, for example, is a set of nodes that contain keys and pointers that are arranged in a hierarchy.
- noncursor function
- A user-defined function that returns only a single group of values and therefore does not require a cursor when it is executed.
- noncursor procedure
- A legacy SPL procedure that returns either a single group of values or no values and therefore does not require a cursor when it is executed. Those SPL routines that return only one row are now noncursor functions because procedures return no values.
- non-variant function
- An external function that always returns the same value when passed the same arguments.
- not null constraint
- A constraint on a column that specifies the column cannot contain null values.
- null value
- A value representing unknown or not applicable. (A null is not the same as a value of zero or blank.)
- object
- See database object.
- object mode
- The state of a database object as recorded in the sysobjstate system catalog table, for example, enabled, disabled, or filtering.
- object-relational database
- A database that adds object-oriented features to a relational database, including support for user-defined types, user-defined routines, complex data types, and inheritance.
- opaque data type
- A fundamental data type you define that contains one or more values encapsulated with an internal length and input and output functions that convert text to and from an internal storage format. Opaque types need user-defined routines and user-defined operators that work on them. Synonym for base type, user-defined base type.
- operator
- In an SQL statement, a symbol (such as =, >, <,+, -, *, and so forth) that invokes an operator function.
- operator binding
- The implicit invocation of an operator function when an operator is used in an SQL statement with user-defined data types.
- operator class
- The set of functions (operators) that INFORMIX-Universal Server associates with a type of secondary access method for query optimization and building the index. Different kinds of operators can be associated with different secondary access methods. See strategy functions and support functions.
- operator function
- A user-defined function that has a corresponding operator symbol. An operator function processes one to three arguments and returns a value. For example, the plus function corresponds to the "+" operator symbol.
- overloading
- See function overloading.
- pad
- Usually a space or blank to fill empty places at the beginning or end of a line, string, or field.
- page
- The basic unit of disk and memory storage used by the database server and whose size is fixed for a particular operating system and platform.
- parallelism
- The ability to process a task in parallel by breaking the task into subtasks and processing the subtasks simultaneously in order to improve performance.
- parameter
- A variable that is given a constant value for a specified application. In a subroutine, a parameter is the placeholder for the argument values that are passed to the subroutine at runtime.
- permission
- On some operating systems, the right to access files and directories.
- pointer
- A number that specifies the "address-in-memory" of the data or variable of interest.
- polymorphism
- See routine overloading and type substitutability.
- predefined opaque data type
- An opaque data type for which the database server provides the type definition. See BLOB, CLOB, BOOLEAN.
- predicate lock
- A lock held on index keys that qualify for a predicate. In a predicate lock, exclusive predicates consist of a single key value, and shared predicates consist of a query rectangle and a scan operation such as inclusion or overlap.
- prepared statement
- An SQL statement that is generated by the PREPARE statement to allow you to form your request while the program is executing without having to modify and recompile the program.
- preprocessor
- A program that takes high-level programs and produces code that a standard language compiler, such as C, can compile.
- primary access method
- A set of routines that perform table operations such as inserting, deleting, updating and scanning data in a table.
- primary key
- The information from a column or set of columns that uniquely identifies each row in a table. The primary key sometimes is called a unique key.
- primary-key constraint
- Specifies that each entry in a column or set of columns contains a non-null unique value.
- privilege
- The right to use or change the contents of a database, table, table fragment, or column. See access privileges.
- procedure overloading
- See routine overloading.
- procedural statement
- A programming language statement that specifies actions; for example, looping and branching if a condition is met. Compare with declaration statement.
- procedure
- A routine that can accept arguments but does not return a value. See external procedure, SPL procedure, user-defined procedure, stored procedure.
- procedure variable
- See variable.
- program block
- A named collection of statements, such as a function, routine, or procedure, that performs a particular task; a unit of program code.
- projection
- Taking a subset from the columns of a single table. Projection is implemented through the select list of a SELECT statement and returns some of the columns and all the rows in a table. See selection.
- R-tree index
- A type of index that uses a tree structure based on overlapping bounding rectangles to speed access to spatial and multi-dimensional data types.
- referential constraint
- Defines the integrity relationship between columns within a table or between tables; also known as a parent-child relationship. Referencing columns also are known as foreign keys.
- relational database
- A database that logically represents all of its information in tables and supports at least the three relational operations known as selection, projection, and join.
- ROLLBACK WORK
- The statement that reverses an action or series of actions on a database. The database is returned to the condition that existed before the actions were executed. See transaction, COMMIT WORK.
- root supertype
- The named row type at the top of a type hierarchy. A root supertype has no supertype above it.
- routine
- A collection of program statements that perform a particular task. Routines include functions, which return one or more values, and procedures, which do not return values. See user-defined routine.
- routine overloading
- The property that allows you to define more than one routine with the same name but different parameter lists. Routine overloading allows you to define routines that have the same name but different arguments and functionality.
- routine resolution
- The process that INFORMIX-Universal Server uses to determine which routine to execute, given the name of the routine, the type of routine (procedure or function), and a list of arguments. In an ANSI-compliant database, the owner is also part of the signature and is used to determine which routine to execute.
- routine signature
- The information that the database server uses to identify a routine. The signature of a routine includes the type of the routine (function or procedure), the routine name, the number of parameters, the data types of the parameters, and the order of the parameters. In an ANSI-compliant database, the name of the routine is specified as owner.name.
- routine -specific name
- See specific name.
- row
- A group of related items of information about a single entity across all columns in a database table. In an object-relational model, each row of a table stands for one instance of the subject of the table, which is one particular example of that entity.
- ROW type
- See unnamed row type.
- row type
- A complex data type that contains one or more related data fields, of any data type, that form a template for a record. The data in a row type can be stored in a row or column. See named row type and unnamed row type.
- row variable
- An INFORMIX-ESQL/C host variable or SPL variable that holds an entire row type and provides access to the individual fields of the row.
- sbspace
- A logical storage area that contains one or more chunks that only store BLOB and CLOB data.
- schema
- The structure of a database or a table. The schema for a table lists the names of the columns, their data types, and (where applicable) the lengths, indexing, and other information about the structure of the table.
- scope
- The part of a routine or application program in which an identifier applies and can be accessed, such as local, global, and modular.
- scroll cursor
- A cursor that can fetch the next row or any prior row, so it can read rows multiple times.
- secondary access method
- A set of server functions to access and manipulate an index. Universal Server provides the B-tree and R-tree secondary access methods; DataBlade Modules provide other secondary access methods.
- select cursor
- A cursor that is associated with a SELECT statement.
- selection
- Taking the horizontal subset of rows of a single table that satisfies a particular condition. This kind of SELECT statement returns some of the rows and all of the columns in a table. Selection is implemented through the WHERE clause of a SELECT statement. See projection.
- selectivity
- The proportion of rows within the table that a query filter can pass.
- sequential cursor
- A cursor that can fetch only the next row in sequence so a sequential cursor can read through a table only once each time the sequential cursor is opened.
- Serializable
- An ANSI level of isolation set with the SET TRANSACTION statement, ensuring all data read during a transaction is not modified during the entire transaction.
- server name
- The unique name of a database server, assigned by a database administrator and used by an application to select a database server.
- server number
- A unique number between 0 and 255, inclusive, assigned by a database administrator to a database server when the server is initialized.
- session
- The structure that is created for an application using the database server.
- SET
- A collection data type created with the SET type constructor, in which elements are not ordered and duplicate values can be inserted.
- set functions
- See aggregate functions.
- shared library
- A library that contains routines that are used by applications, are loaded into memory by the operating system as they are needed, and are shared with other applications.
- shared lock
- A lock that more than one thread can acquire on the same object, allowing for greater concurrency with multiple users.
- shared memory
- A portion of main memory that more than one process can use at a time so that processes can communicate and share common data, thus reducing disk I/O and improving performance.
- signature
- See routine signature.
- simple blob
- Synonym for simple large object.
- simple large object
- A large object that is stored in a blobspace, is not recoverable, and does not obey transaction isolation modes. Simple large objects include TEXT and BYTE data types.
- simple predicate
- A search condition in the WHERE clause that has one of the following forms: f(column, constant), f(constant, column), or f(column), where f is a binary or unary function that returns a Boolean value (TRUE, FALSE, or UNKNOWN).
- singleton SELECT
- A statement that returns a single row.
- smart large object
- A large object that is stored in an sbspace, has read, write, and seek properties similar to a UNIX file, is recoverable, obeys transaction isolation modes, and can be retrieved in segments by an application. Smart large objects include CLOBs and BLOBs.
- SMI
- Acronym for System Monitoring Interface.
- source file
- A file containing instructions (in ASCII text) that is used as the source for generating compiled programs.
- specific name
- A unique identifier that you define with the SPECIFIC keyword in a CREATE PROCEDURE or CREATE FUNCTION statement to serve as an alternate name for a routine. In an ANSI-compliant database, the specific name must be unique within the schema. In a database that is not ANSI-compliant, the specific name must be unique within the database. A specific name is distinct from the name of the actual routine. A routine that has been overloaded can be uniquely identified by its specific name. A specific name can be used with the DROP, GRANT, REVOKE, and UPDATE STATISTICS.
- SPL
- Acronym for Stored Procedure Language, an Informix extension to SQL that provides flow control features such as sequencing, branching, and looping, comparable to those provided in the SQL/PSM standard.
- SPL function
- An SPL routine that can accept arguments and returns one or more values.
- SPL procedure
- An SPL routine that can accept arguments and may update the database, but does not return a value.
- SPL routine
- A routine written in Stored Procedure Language (SPL) and SQL that is parsed, optimized, and stored in the system catalog tables in executable format. SPL routines include SPL procedures and SPL functions.
- SPL variable
- A variable defined and used in an SPL routine.
- SQL API
- An API that provides a library of functions to an Informix client application, such as an INFORMIX-ESQL/C application, so it can access a database server through embedded SQL and function calls. See Client API.
- statement
- A line, or set of lines, of program code that describes a single action (for example, a SELECT statement or an UPDATE statement).
- statement block
- A section of a program that usually begins and terminates with special symbols such as begin and end. A statement block is the smallest unit of scope of reference for program variables.
- statement identifier
- An embedded variable name or SQL statement identifier that represents a data structure defined in a PREPARE statement. A statement identifier is used for dynamic SQL statement management by Informix SQL APIs.
- status variable
- A program variable that indicates the status of some aspect of program execution. Status variables often store error numbers or act as flags to indicate that an error has occurred.
- stored function
- See user-defined function.
- stored procedure
- A term used in earlier versions of Informix products for SPL procedures and SPL functions. See SPL routine, SPL procedure, and SPL function.
- Stored Procedure Language
- See SPL, SPL routine.
- strategy functions
- The functions that the optimizer uses to decide what filters in a query can use a secondary access method (index).
- subquery
- A SELECT statement within a WHERE clause.
- subtable
- A typed table that inherits properties (column definitions, constraints, triggers) from a supertable above it in the table hierarchy and can add additional properties.
- subtype
- A named row type that inherits all representation (data fields) and behavior (routines) from a supertype above it in the type hierarchy and can add additional fields and routines. The number of fields in a subtype is always greater than or equal to the number of fields in its supertype.
- supertable
- A typed table whose properties (constraints, storage options, triggers) are inherited by a subtable beneath it in the table hierarchy. The scope of a query on a supertable is the supertable and its subtables.
- supertype
- A named row type whose representation (data fields) and behavior (routines) is inherited by a subtype below it in the type hierarchy.
- support functions
- The functions that INFORMIX-Universal Server automatically invokes to process a data type.
1) The database server uses a support function to perform operations (such as converting to and from the internal, external, and binary representations of the type) on opaque data types.
2) An index access method uses a support function in an operator class to perform operations (such as building or searching) on an index.
- sysmaster database
- A database that each database server has and that holds the catalog tables and system monitoring interface (SMI) tables.
- system catalog
- A group of database tables that contain information about the database itself, such as the names of tables or columns in the database, the number of rows in a table, the information about indexes and database privileges, and so on.
- system-defined cast
- A cast that is built in to the database server. A system-defined casts performs automatic conversions between different built-in data types.
- System Monitoring Interface
- A collection of tables in the sysmaster database that maintains dynamically updated information about the operation of the database server.
- table
- A rectangular array of data in which each row describes a single entity and each column contains the values for each category of description. A table is sometimes referred to as a base table to distinguish it from the views, indexes, and other objects defined on the underlying table or associated with it.
- table hierarchy
- A relationship you can define among typed tables in which subtables inherit the behavior (constraints, triggers, storage options) from supertables. Subtables can add additional constraint definitions, storage options, and triggers.
- table inheritance
- The property that allows a typed table to inherit the behavior (constraints, storage options, triggers) from a typed table above it in the table hierarchy.
- TEXT
- A data type for a simple large object that stores text and can be as large as 231 bytes.
- transaction
- A collection of one or more SQL statements that are treated as a single unit of work and are committed or rolled back together.
- transaction lock
- A lock on an R-tree index that is obtained at the beginning of a transaction and held until the end of the transaction.
- transaction logging
- The process of keeping records of transactions. See logical log.
- transaction mode
- The method by which constraints are checked during transactions. You use the SET statement to specify whether constraints are checked at the end of each data manipulation statement or after the transaction is committed.
- trigger
- A mechanism that resides in the database and specifies that when a particular action (insert, delete, or update) occurs on a particular table, the database server should automatically perform one or more additional actions.
- type constructor
- An SQL keyword that indicates to the database server the type of complex data to create (for example, ROW, SET, MULTISET, LIST).
- type hierarchy
- A relationship that you define among named row types in which subtypes inherit representation (data fields) and behavior (routines) from supertypes and can add additional fields and routines.
- type inheritance
- The property that allows a named row type or typed table to inherit representation (data fields, columns) and behavior (routines, operators, rules) from a named row type above it in the type hierarchy
- type substitutability
- The ability to use an instance of a subtype when an instance of its supertype is expected.
- typed collection variable
- An ESQL/C collection variable or SPL variable that has a defined collection data type associated with it and can only hold a collection of its defined type. See untyped collection variable.
- typed table
- A table that is constructed from a named row type and whose rows contain instances of that row type. A typed table can be used as part of a table hierarchy. The columns of a typed table correspond to the fields of the named row type.
- unique constraint
- Specifies that each entry in a column or set of columns has a unique value.
- unique index
- An index that prevents duplicate values in the indexed column.
- unique key
- See primary key.
- unnamed row type
- A row type created with the ROW constructor that has no defined name and no inheritance properties. Two unnamed row types are equivalent if they have the same number of fields and if corresponding fields have the same data type, even if the fields have different names.
- untyped collection variable
- A generic ESQL/C collection variable or SPL variable that can hold a collection of any collection data type and takes on the data type of the last collection assigned to it. See typed collection variable.
- user-defined base type
- See opaque data type.
- user-defined data type
- A data type that you define for use in a Universal Server database. You can define opaque data types and distinct data types.
- user-defined function
- A user-defined routine that returns a value. A user-defined function can be a support function or an end-user function.
- user-defined routine
- A routine that is not included with the database server or DataBlade module, whose name and parameters are registered in the system catalog tables, and that can be invoked by an SQL statement or another routine. A user-defined routine can be written in an external language (external routine) or in SPL (SPL routine).
- user-defined procedure
- A user-defined routine that does not return a value. A user-defined procedure cannot be a support routine because all support routines return values.
- user ID
- See Informix user ID.
- user ID password
- See Informix user password.
- user name
- See Informix user ID.
- user password
- See Informix user password.
- variable
- The identifier for a location in memory that stores the value of a program object whose value can change during the execution of the program.
- view
- A dynamically controlled picture of the contents in a database that allows a programmer to determine what information the user sees and manipulates. A view represents a virtual table based on a specified SELECT statement.
- violations table
- A special table that holds rows that fail to satisfy constraints and unique index requirements during data manipulation operations on base tables. You use the START VIOLATIONS TABLE statement to create a violations table and associate it with a base table.
- virtual column
- A derived column of information that is not stored in the database but that is created in an SQL statement by manipulating or combining database columns.
- virtual processor
- One of the multithreaded processes that make up the database server and are similar to the hardware processors in the computer.
- virtual table
- A table whose data that you create to access external data in a file or database that is not managed by Universal Server. The Virtual Table Interface allows Universal Server users to access the external data in a virtual table using SQL DML statements and join the external data with Universal Server table data.
- white space
- A series of one or more space characters. The locale file defines what characters are considered to be space characters.
- wildcard
- A special symbol, such as an asterisk or question mark, represents any sequence of zero or more characters or any single character in an SQL statement, operating system command, or program language statement.
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