Glossary: Glossary

Glossary

ACB (Application Control Block): a DL/I control block that contains the combined information from the Database Descriptions (DBDs) and Program Specification Blocks (PSBs).
ACBLIB: the data set that contains the DL/I Application Control Blocks. See also Application Control Block (ACB).
access descriptor: a SAS/ACCESS file that describes data that is managed by SAS, by a database management system, or by a PC-based software application such as Microsoft Excel, Lotus 1-2-3, or dBASE. After creating an access descriptor, you can use it as the basis for creating one or more view descriptors. See also SAS/ACCESS view, view descriptor.
Application Control Block: See ACB (Application Control Block).
attach parameter list: a set of parameters that are passed to DL/I when the IMS engine or the IMS DATA step interface is executed in a DL/I environment. The parameters vary for each region type. Most parameters can be modified with SAS system options that are specified for the SAS/ACCESS interface to IMS.
batch mode: a method of executing SAS programs in which a file that contains SAS statements plus any necessary operating environment commands is submitted to the computer's batch queue. After you submit the program, control returns to your computer, and you can perform other tasks. Batch mode is sometimes referred to as running in the background. The program output can be written to files or printed on an output device.
batch region: a DL/I processing environment for running batch mode jobs to access DL/I databases. Database data sets must be allocated to this region. A batch region is supervised by the DL/I batch control program.
BMP (Batch Message Processing) region: a DL/I processing environment in IMS/ESA DB/DC subsystems and in CICS for running batch programs that access active online DL/I databases and message queues, as well as non-DL/I data sets. Database data sets are allocated to an online control region, not to the BMP region.
browsing data: the process of viewing the contents of a file. Depending on how the file is accessed, you can view SAS data either one observation (row) at a time or as a group in a tabular format. You cannot update data that you are browsing.
call (DL/I): a request made by the IMS-DL/I engine to DL/I to access one or more segments of a database or message queue, or to perform some system function.
checkpoint: the result of a CHKP call. A checkpoint establishes a synchronization point in the execution of the program. A synchronization point is used by DL/I backout services to determine which updates to back out (cancel) in the event of an abend or system crash. The program must be restarted at the synchronization point.
checkpoint ID: an eight-byte value that is written to the DL/I log record to identify a program checkpoint.
child: in a hierarchical database, a segment that is the direct dependent of another segment, which is called the child's parent. The data in a dependent segment relies on the parent segment and on all higher segments for complete identification and qualification.
command code: a special indicator that is used in a Segment Search Argument (SSA) to modify the type of call that is being issued. The most commonly used command code is the D code, which is used to issue a path call.
commit: the process that ends a transaction and that makes permanent any changes to the database that the user made during the transaction.
DATA step: in a SAS program, a group of statements that begins with a DATA statement and that ends with either a RUN statement, another DATA statement, a PROC statement, the end of the job, or the semicolon that immediately follows lines of data. The DATA step enables you to read raw data or other SAS data sets and to use programming logic to create a SAS data set, to write a report, or to write to an external file.
DATA step view: a type of SAS data set that consists of a stored DATA step program. A DATA step view contains a definition of data that is stored elsewhere; the view does not contain the physical data. The view's input data can come from one or more sources, including external files and other SAS data sets. Because a DATA step view only reads (opens for input) other files, you cannot update the view's underlying data.
data type: an attribute of every column in a table or database. The data type tells the operating system how much physical storage to set aside for the column and specifies what type of data the column will contain. It is similar to the type attribute of SAS variables.
data value: the intersection of a row (observation) and a column (variable) in the rectangular form of a SAS data set.
database: an organized collection of related data. A database usually contains named files, named objects, or other named entities such as tables, views, and indexes.
Database Description: See DBD (Database Description).
database management system: See DBMS (database management system).
Database Recovery Control: See DBRC (Database Recovery Control).
DBA (Database Administrator): the person who is responsible for developing and maintaining database management systems at a computer site.
DBB region: a DL/I batch processing environment for running programs that can access DL/I databases as well as non-DL/I data sets. In a DBB region, DL/I accesses the ACBLIB in order to obtain control block information.
DBD (Database Description): a DL/I control block that defines the hierarchical data structure and the physical characteristics of a database to DL/I.
DBDGEN: the utility procedure that generates Database Descriptions (DBDs).
DBDLIB: a data set that contains Database Descriptions (DBDs).
DBMS (database management system): a software application that enables you to create and manipulate data that is stored in the form of databases.
DBRC (Database Recovery Control): an IMS facility that controls the restoration of databases after a system failure. DBRC also supports data sharing among IMS/ESA subsystems.
dependent segment: a segment that has a parent segment. The data in a dependent segment relies on the parent segment and on all higher segments for complete identification and qualification. See also segment.
DL/I (Data Language/I): the IBM database language for IMS/VS, CICS/OS/VS, CICS/DOS/VS, and DL/I DOS/VS systems.
DLI region: a DL/I batch processing environment for running programs that can access DL/I databases as well as non-DL/I data sets. No access to message queues is possible. In a DLI region, DL/I accesses the DBDLIB and PSBLIB for control block information.
editing data: the process of viewing the contents of a file with the intent and the ability to change those contents. Depending on how the file is accessed, you can view the data either one observation at a time or in a tabular format.
engine: a component of SAS software that reads from or writes to a file. Each engine enables SAS to access files that are in a particular file format.
feedback data: the data that is returned to the IMS engine (usually in the PCB mask) after a DL/I call has been issued.
field: in a hierarchical database, the smallest unit of data storage.
file: a collection of related records that are treated as a unit. SAS files are processed and controlled by SAS and are stored in SAS libraries.
format: a pattern or set of instructions that SAS uses to determine how the values of a variable (or column) should be written or displayed. SAS provides a set of standard formats and also enables you to define your own formats.
Get call: a DL/I call that retrieves one or more segments so that the contents of the segments can be read by the IMS engine.
hierarchical database: a database that is organized as a tree structure of segments. A DL/I database has a hierarchical data structure.
hierarchical sequence: the standard processing sequence for segments of a database record. The sequence is basically top-to-bottom, front-to-back, and left-to-right.
hierarchical structure: an arrangement of data in which records occur at distinct levels, with different types of information at each level. Records are related to other records as ancestors, descendants, siblings, and so on.
I/O area: a data structure in which the IMS-DL/I engine holds retrieved segments for processing or output.
I/O PCB (Input/Output Program Communication Block): a type of DL/I control block that communicates information about non-database access requests. See also PCB (Program Communication Block).
IMS/ESA: Information Management System/Enterprise System Architecture. IMS/ESA is an IBM database management system that uses the DL/I database language.
IMS/ESA Resource Lock Manager: See IRLM (IMS/ESA Resource Lock Manager).
index: a component of a SAS data set that enables SAS to access observations in the SAS data set quickly and efficiently. The purpose of SAS indexes is to optimize WHERE-clause processing and to facilitate BY-group processing.
interactive line mode: a method of running SAS programs in which you enter one line of a SAS program at a time at the SAS session prompt. SAS processes each line immediately after you press the ENTER or RETURN key. Procedure output and informative messages are returned directly to your display device.
interface view engine: a SAS engine that retrieves data directly from files that have been formatted by another vendor's software and which presents the data to SAS in the form of a SAS data set. Interface view engines are transparent to users and are not specified in LIBNAME statements. See also engine.
IRLM (IMS/ESA Resource Lock Manager): a facility for ensuring database integrity among multiple DL/I subsystems.
key field: a field that identifies and provides access to an occurrence of a segment. A key field is also called a sequence field.
libref (library reference): a short name (or alias) for the full physical name of a SAS library. A SAS LIBNAME statement maps the libref to the full physical name. A libref is the first part of a multi-level SAS filename and indicates the SAS library in which a SAS file is stored. For example, in the name SASUSER.ACCTS, SASUSER is the libref, and ACCTS is a file in the library that the SASUSER libref refers to. See also SAS library.
logical database: a collection of database segments from one or more physical databases. A logical database enables the IMS-DL/I engine to view a database structure that is different from the physical structure.
member: a SAS file in a SAS library.
member name: a name that is assigned to a SAS file in a SAS library. See also member type.
member type: a SAS name that identifies the type of information that is stored in a SAS file. Member types include ACCESS, AUDIT, DMBD, DATA, CATALOG, FDB, INDEX, ITEMSTOR, MDDB, PROGRAM, UTILITY, and VIEW.
missing value: in SAS, a term that describes the contents of a variable that contains no data for a particular row or observation. By default, SAS prints or displays a missing numeric value as a single period, and it prints or displays a missing character value as a blank space.
noninteractive mode: a method of running SAS programs in which you prepare a file of SAS statements and submit the program to the operating system. The program runs immediately and occupies your current session.
observation: a row in a SAS data set. All of the data values in an observation are associated with a single entity such as a customer or a state. Each observation contains either one data value or a missing-value indicator for each variable. An observation is analogous to a row in a database table. However, unlike rows in a database table or file, observations in a SAS data file have an inherent order.
online access region: a DL/I processing environment for running batch programs that can access active online DL/I databases. The only type of online access region that the SAS/ACCESS interface to IMS supports is the BMP region.
parent: in a hierarchical database, a segment that has one or more dependent segments, which are called its children. The data in a dependent segment rely on the parent segment and on all higher segments for complete identification and qualification.
path: a single route through a database, following the hierarchical sequence of segments from a higher-level segment to a lower-level segment.
path call: a DL/I call to a database that returns multiple segments from a hierarchical path.
PCB (Program Communication Block): a DL/I control block that defines either a message queue or the part of a database that can be accessed by the IMS-DL/I engine. A PCB is part of a Program Specification Block (PSB).
PCB mask: a data structure to which DL/I returns information about the DL/I calls that an application issues.
physical database: a collection of database segments in a specified hierarchical structure. These segments are organized according to a particular DL/I access method.
PROC SQL view: a SAS data set that is created by the SQL procedure. A PROC SQL view contains no data. Instead, it stores information that enables it to read data values from other files, which can include SAS data files, SAS/ACCESS views, DATA step views, or other PROC SQL views. A PROC SQL view's output can be either a subset or a superset of one or more files. See also SAS data view.
PROC step: a group of SAS statements that call and execute a SAS procedure. A PROC step usually takes a SAS data set as input.
Program Communication Block: See PCB (Program Communication Block).
Program Specification Block: See PSB (Program Specification Block).
program view: the part of a database that the IMS-DL/I engine can access. The Program Communication Block (PCB) establishes the program view.
PSB (Program Specification Block): a DL/I control block that defines the DL/I resources that are used by the IMS-DL/I engine. Each database that the IMS-DL/I engine uses is defined by a separate Program Communication Block (PCB) within the PSB.
PSBGEN: the process that generates Program Specification Blocks (PSBs
PSBLIB: the data set that contains the Program Specification Blocks (PSBs).
qualified call: a DL/I call that specifies at least one Segment Search Argument (SSA). See also Segment Search Argument (SSA).
qualified SSA: a Segment Search Argument that contains one or more qualification statements to specify search criteria for locating particular segment occurrences. See also Segment Search Argument (SSA).
random access: an access mode that is used by the IMS engine or by the IMS DATA step interface. This access mode is used when a WHERE statement is specified from which the engine can generate Segment Search Arguments. In the SAS/ACCESS interface to IMS-DL/I, the distinction between sequential access and random access differs from that of some other programming languages.
read integrity: a characteristic of database management systems in which database access is controlled so that two programs cannot access a record simultaneously if one of the programs is requesting update access. Read integrity guarantees that the data is always current when read access is granted. See also update integrity.
region type: the kind of DL/I processing environment. The IMS engine uses two categories of region types: batch regions (DLI or DBB) and online access regions (BMP).
relational database management system: a database management system that organizes and accesses data according to relationships between data items. The main characteristic of a relational database management system is the two-dimensional table. Examples of relational database management systems are DB2, Oracle, SYBASE, and Microsoft SQL Server.
restart: the process of resuming an interrupted program without repeating completed transactions.
restricted option: a SAS system option that has been installed at your site such that its default setting cannot be overridden by applications programmers.
return code: a code that is passed to the operating system and that indicates whether a command or a job step has executed successfully.
root segment: the highest-level segment in a database.
SAS data file: a type of SAS data set that contains data values as well as descriptor information that is associated with the data. The descriptor information includes information such as the data types and lengths of the variables, as well as the name of the engine that was used to create the data. See also SAS data set, SAS data view.
SAS data set: a file whose contents are in one of the native SAS file formats. There are two types of SAS data sets: SAS data files and SAS data views. SAS data files contain data values in addition to descriptor information that is associated with the data. SAS data views contain only the descriptor information plus other information that is required for retrieving data values from other SAS data sets or from files whose contents are in other software vendors' file formats.
SAS data view: a type of SAS data set that retrieves data values from other files. A SAS data view contains only descriptor information such as the data types and lengths of the variables (columns), plus other information that is required for retrieving data values from other SAS data sets or from files that are stored in other software vendors' file formats. SAS data views can be created by the SAS DATA step and by the SAS SQL procedure.
SAS library: a collection of one or more files that are recognized by SAS and that are referenced and stored as a unit. Each file is a member of the library.
SAS/ACCESS view: a type of file that retrieves data values from files that are stored in other software vendors' file formats. You use the ACCESS procedure of SAS/ACCESS software to create SAS/ACCESS views. See also view descriptor.
search field: a field that is defined to DL/I in the Database Description (DBD) and which can be used to search for particular segments. A search field does not uniquely identify the segment.
segment: in a DL/I database, a grouping of related data items in a database structure. The segment is the unit of data that can be accessed by the IMS engine or by the IMS DATA step interface.
segment level: the relative distance of a particular segment from the root segment along a hierarchical path. The segment level is usually represented numerically, with the root segment at level 1 and its immediate dependents at level 2.
segment occurrence: in a DL/I database, a specific instance in a set of segments that have the same segment type.
Segment Search Argument: See SSA (Segment Search Argument).
segment type: in a DL/I database, a category of related data elements. There can be multiple segment occurrences for a particular segment type.
sensitive segment: a segment in a DL/I database that the IMS engine or the IMS DATA step interface can access. A segment is defined as sensitive for a particular program in the Program Specification Block (PSB).
sequence field: another term for key field. See key field.
sequential access: a method of file access in which the records are read or written one after the other from the beginning of the file to the end. Sequential access is the default access mode that the IMS engine uses to retrieve all segments down one path of a database. In the SAS/ACCESS interface to IMS, the distinction between sequential access and random access differs somewhat from that of other programming languages.
siblings: in a hierarchical database, segments that have the same parent segment.
SQL (Structured Query Language): a standardized, high-level query language that is used in relational database management systems to create and manipulate database management system objects. SAS implements SQL through the SQL procedure.
SSA (Segment Search Argument): the formatted search criteria that are passed to DL/I in order to identify a particular segment or group of segments to be processed. Multiple SSAs can be specified in one DL/I call.
status code: a two-byte indicator field that DL/I returns to indicate the relative success of an attempted call.
subsystem: a complete DL/I configuration, including the DL/I region controller and service modules, the DL/I databases, and the IMS engine.
synchronization point: a time at which a) all update commands that have been successfully executed and applied since the previous synchronization point was established are committed to the database and b) all DL/I resources that have been held since the previous synchronization point was established are released. Synchronization points are established by issuing CHKP calls. By default, the SAS IMS engine generates and submits a CHKP call at the end of a PROC step or DATA step, whereas the DATA step interface to IMS generates and submits explicit CHKP calls as coded by the application logic. Synchronization points can be used to resume the processing of an interrupted job. See also commit.
twins: segments that represent multiple occurrences of the same segment type under a single parent.
uncommitted: See commit.
undefined field: a field that is not defined to DL/I in a Database Description (DBD). An undefined field is neither a sequence field nor a search field. The segment cannot be accessed by specifying this field to DL/I.
unqualified call: a DL/I call that contains no Segment Search Argument (SSA). See also SSA (Segment Search Argument).
unqualified SSA: a Segment Search Argument that specifies a segment type only. See also SSA (Segment Search Argument).
update call: a DL/I call that signals the intent to alter (modify, delete, or add) information in the database.
update integrity: a characteristic of a database management system in which database access is controlled so that two programs cannot access a record simultaneously if both programs are requesting update access. Update integrity guarantees that data is always current when update access is granted. However, it does not guarantee that data is always current when read access is granted. See also read integrity.
variable: a column in a SAS data set or in a SAS data view. The data values for each variable describe a single characteristic for all observations (rows). Each SAS variable can have the following attributes: name, data type (character or numeric), length, format, informat, and label. In the ACCESS procedure, variables are created from the database product's columns or fields.
view descriptor: a SAS/ACCESS file that defines part or all of the DBMS data that is described by an access descriptor. See also access descriptor.

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