Access File
|
An optional FOCUS file description available in the DBCTL
environment. It identifies the PSB to use with a request.
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ACB
|
Application Control Block. Optimized PSB. Contains consolidated
information from the PSB and DBD. Speeds up online
processing. Created by an ACBGEN.
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BMP
|
Batch Message Processing. Batch job with access to online
resources.
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Concatenated key
|
Concatenated key values of all segments along the hierarchical
path to a particular segment instance.
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Control Region
|
IMS address space that controls the IMS system. Maintains
order among terminals, databases, and application programs in
the online environment.
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CCTL
|
Coordinating Controller. Transaction manager used with a
DBCTL.
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CICS
|
Customer Information Control System.
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Current database
position
|
The segment retrieved by the most recent DL/I call.
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Data sensitive
|
IMS has access to the data in the segment, not just to its key.
See also Key sensitive.
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DBCTL
|
DB Control. Control region used in a DB-only system.
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DBD
|
Database Description. Physical structure of the database.
Created by a DBDGEN.
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DBRC
|
Database Recovery Control.
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DDIR
|
DMB Directory. Directory of databases.
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DEDB
|
Data Entry Database. A type of Fast Path database.
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Dependent Region
|
IMS address space responsible for processing transactions
scheduled for it by the control region. The application program is
executed in this region.
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DL/I
|
Data Language I (one). Language for accessing IMS databases.
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DLISAS
|
DL/I Separate Address Space. Address space responsible for
database handling.
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DMB
|
Data Management Block. Optimized DBD.
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EMH
|
Expedited Message Handling. Fast Path transactions.
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Fast Path
|
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.
|
Field level
sensitivity
|
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.
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FOCPSB
|
A required FOCUS file description that describes the PSB and
associates Master Files with the PCBs in the PSB.
|
GN
|
Get Next. DL/I sequential read.
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GU
|
Get Unique. Non-sequential DL/I retrieval call.
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HDAM
|
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.
|
HIDAM
|
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.
|
Hierarchical
sequence
|
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 child's first child, down to the lowest
level; then it proceeds up one level and follows the next
segment down through its children, and so on.
|
Hierarchical path
|
Consists of a segment and all of its ancestors starting from the
root.
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HISAM
|
Hierarchical Indexed Sequential Access Method. In a HISAM
database there are two datasets: a primary indexed dataset that
contains the root and most of the dependent segments from
each record, and an overflow sequential dataset that contains
the rest of each record. Segments within a record are
associated by physical adjacency.
|
HSAM
|
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.
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IFP
|
IMS Fast Path. Region for EMH transactions.
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IMS
|
Information Management System.
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IMS/DB
|
IMS Database Manager. Stand-alone product in V4R1.
|
IMS/DC
|
IMS Database Communications. Old name for terminal/
transaction handler.
|
IMS/ESA
|
IMS/Enterprise Systems Architecture (V3,V4). Designed for
MVS/ESA.
|
IMS/TM
|
IMS Transaction Manager. New name for terminal/transaction
handler.
|
Key
|
A field in a segment that defines the segment's order within its
twin chain.
|
Key feedback area
|
Area of a PCB for storing the concatenated key of a segment
retrieved by a DL/I call.
|
Key sensitive
|
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.
|
IRLM
|
Inter-Region Lock Manager or IMS Resource Lock Manager.
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Master File
|
A required FOCUS file description that describes the segments
and fields accessible through a particular PCB.
|
Optimization
|
The process in which the Interface passes the record selection
criteria of a FOCUS report request to IMS for processing.
|
PCB
|
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.
|
PSB
|
Program Specification Block. Defines the IMS resources needed
by an application program. Contains PCBs. Created by a
PSBGEN.
|
Qualified SSA
|
An SSA that contains selection criteria on search and/or
sequence fields. IMS retrieves only those segments that satisfy
the criteria.
|
Root segment
|
Unique segment at the top of the hierarchical tree.
|
Search field
|
A field listed in the DBD. Does not have to be a sequence field.
It can be used in qualified SSAs.
|
Segment Code
|
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.
|
Sensitive field
|
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.
|
Sequence field
|
Key field. Identifies a segment.
|
Short path
|
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.
|
SSA
|
Segment Search Argument. Describes the segments IMS should
retrieve.
|
Subtree
|
A subset of the database that cannot include a segment without
its parent.
|
Symbolic pointer
|
Concatenated key values of all segments along the hierarchical
path up to and including the segment pointed to.
|
Twins
|
Segment instances of the same type and with the same parent.
|
Unique key
|
A key that fully identifies a segment. No other segment can have
the same key value.
|
Unique segment
|
A segment with no twins; has a one-to-one relationship with its
parent.
|
Unqualified SSA
|
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.
|