An optional FOCUS file description available in the DBCTL environment. It identifies the PSB to use with a request.

Application Control Block. Optimized PSB. Contains consolidated information from the PSB and DBD. Speeds up online processing. Created by an ACBGEN.

Batch Message Processing. Batch job with access to online resources.

Concatenated key values of all segments along the hierarchical path to a particular segment instance.

IMS address space that controls the IMS system. Maintains order among terminals, databases, and application programs in the online environment.

Coordinating Controller. Transaction manager used with a DBCTL.

Customer Information Control System.

The segment retrieved by the most recent DL/I call.

IMS has access to the data in the segment, not just to its key. See also Key sensitive.

DB Control. Control region used in a DB-only system.

Database Description. Physical structure of the database. Created by a DBDGEN.

Database Recovery Control.

DMB Directory. Directory of databases.

Data Entry Database. A type of Fast Path database.

IMS address space responsible for processing transactions scheduled for it by the control region. The application program is executed in this region.

Data Language I (one). Language for accessing IMS databases.

DL/I Separate Address Space. Address space responsible for database handling.

Data Management Block. Optimized DBD.

Expedited Message Handling. Fast Path transactions.

Special IMS access methods that provide enhanced data reliability, availability, and improved response time, but place limitations on the database structure and ability to take advantage of techniques like secondary indexing and logical relationships.

Only the specific fields listed in the PCB are accessible to the application program. If no fields are listed in the PCB, the entire segment is accessible.

A FOCUS file description that describes the PSB and associates Master Files with the PCBs in the PSB.

Get Next. DL/I sequential read.

Get Unique. Non-sequential DL/I retrieval call.

Hierarchical Direct Access Method. Uses a randomizer or hashing routine to process the root key. Access to dependent segments is through pointers. Random access to roots is quick, but IMS cannot retrieve them sequentially in root key order.

Hierarchical Indexed Direct Access Method. Access to root segments is through an index. The index is a separate database from the data. Can process records in root key sequence, but the need to read the index database as well as the data database slows access. Access to dependent segments is the same as in HDAM databases.

The order in which IMS accesses segments in a database. The hierarchical sequence proceeds from the root, to the first child of the root segment, to the first child of that child, down to the lowest level. Then it proceeds up one level and follows the next segment down through its children, and so on.

Consists of a segment and all of its ancestors starting from the root.

Hierarchical Indexed Sequential Access Method. In a HISAM database there are two data sets, a primary indexed data set that contains the root and most of the dependent segments from each record, and an overflow sequential data set that contains the rest of each record. Segments within a record are associated by physical adjacency.

Hierarchical Sequential Access Method. Relates segments by physically placing them in hierarchical order. Needs static data. A GU call produces a sequential scan from the beginning of the database.

IMS Fast Path. Region for EMH transactions.

Information Management System.

IMS Database Manager. Stand-alone product in V4R1.

IMS Database Communications. Old name for terminal/transaction handler.

IMS/Enterprise Systems Architecture (V3,V4). Designed for MVS/ESA.

IMS Transaction Manager. New name for terminal/transaction handler.

A field in a segment that defines the order of the segment within its twin chain.

Area of a PCB for storing the concatenated key of a segment retrieved by a DL/I call.

IMS has access to the key of the segment, not the data in the segment. Used when a segment has no data of interest, but a lower level segment does. Indicated by PROCOPT=K in the PCB. See also Data sensitive.

Inter-Region Lock Manager or IMS Resource Lock Manager.

A required FOCUS file description that describes the segments and fields accessible through a particular PCB.

The process in which the adapter passes the record selection criteria of a FOCUS report request to IMS for processing.

Program Communication Block. There are two types, database and TP. A database PCB identifies a particular database and contains status information about calls made to the database. It also defines the segments within the database that the application program can access and the types of processing allowed. A TP PCB (also called an I/O PCB) contains status information about calls from the terminal it points to.

Program Specification Block. Defines the IMS resources needed by an application program. Contains PCBs. Created by a PSBGEN.

An SSA that contains selection criteria on search and/or sequence fields. IMS retrieves only those segments that satisfy the criteria.

Unique segment at the top of the hierarchical tree.

A field listed in the DBD. Does not have to be a sequence field. It can be used in qualified SSAs.

A field in the segment that identifies its type. The DBDGEN assigns the type sequentially, starting with 01 for the root, and incrementing by 1 for each SEGM macro in the DBD.

A field listed in the PCB. Fields omitted from the list are not available to the application program. If the PCB lists no fields, the whole segment is accessible.

Key field. Identifies a segment.

A segment that has no instance of its child segment type, or a segment in the host file of a join with no matching segment in the cross-referenced file.

Segment Search Argument. Describes the segments IMS should retrieve.

A subset of the database that cannot include a segment without its parent.

Concatenated key values of all segments along the hierarchical path up to and including the segment pointed to.

Segment instances of the same type and with the same parent.

A key that fully identifies a segment. No other segmen instance can have the same key value.

A segment with no twins. It has a one-to-one relationship with its parent.

An SSA that names the segment type to retrieve but does not specify additional selection criteria. Any segment of the named type satisfies the SSA.