Introduction of Adabas

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ADABAS IS . . .
ADABAS, the ADAptable DataBASe, is a high-performance, multithreaded, database
management system for mainframe platforms where database performance is a critical factor.
It is interoperable, scalable, and portable across multiple, heterogeneous platforms including
mainframe, midrange, and PC.
Operational Highlights
High Availability
ADABAS is designed for operation 7 days a week and 24 hours a day. Space is managed
dynamically (see page 14), files can be loaded and unloaded, backed up and restored, and system
performance can be analyzed without interrupting the active database.
Storage Space Optimization
ADABAS stores data in compressed form to reduce space requirements. Since modern
databases can be measured in gigabytes (1000 megabytes) or even terabytes (1000 gigabytes),
the savings in disk space can be considerable. Reduced space requirements also mean that the
input/output (I/O) system is more efficient.
Performance
Performance is the key factor of ADABAS, which includes a number of features to enhance it.
For instance, a number of set-up parameters are available for fine-tuning the database operating
environment, and many of these can be modified while the database is active.
Fault Tolerance
ADABAS recovers automatically after an abnormal database or system termination. Each time
an ADABAS database is started, an automatic check is initiated to determine whether the
database previously terminated “cleanly” or an active transaction was interrupted. If a
transaction was interrupted, ADABAS automatically resets all changes of the uncompleted
transaction so that the database is consistent.
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Operating Environment
ADABAS 6.2 for mainframes supports the following operating environments:
􀀀 SNI’s BS2000
􀀀 IBM’s OS/390, MVS/ESA, VSE/ESA, and VM/ESA
􀀀 Fujitsu’s OS IV/F4 MSP
􀀀 Software Pursuits’ MVT/VSE
Mainframe ADABAS can be used in distributed environments with ADABAS on
􀀀 Digital’s VAX and Alpha AXP under OpenVMS
􀀀 IBM’s AS/400 under OS/400
􀀀 Wang under VS
􀀀 IBM’s PC and compatibles under OS/2 or Windows/NT
􀀀 a variety of supported UNIX platforms
As the telecommunication interface, mainframe ADABAS supports TP monitors such as
Software AG’s COM-PLETE; or the popular TSO, CICS, IMS/DC, AITM/DC, TIAM, UTM,
or SHADOW.
Software AG’s multisystem processing tool ENTIRE NET–WORK provides the benefits of
distributed processing and (with ADABAS STAR) database distribution by allowing you to
communicate across a network with ADABAS and other service tasks.
Support for network access methods is implemented in the form of line drivers. Mainframe
ENTIRE NET–WORK provides drivers for VTAM, IUCV, DCAM, CTCA (channel-to-channel
adapter), TCP/IP, and XCF.
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Supported Data Models
ADABAS is a “relational-like” database. It is similar to relational databases in that it stores
information in tables in which rows represent individual data records and columns represent
fields. As in relational databases, separate ADABAS files can be linked logically by a common
field.
ADABAS differs from true relational databases in that it
􀀀 stores many data relationships physically, resulting in fewer demands on CPU resources than
true relational databases, which create all relationships logically at runtime.
􀀀 supports repeating groups of fields.
ADABAS separates data relationships, management, and retrieval from the actual physical data
and stores the physical data independently. It provides flexible access techniques and performs
both simple and complex searches quickly and efficiently. The independence of the data from
the program minimizes the need to reprogram when the database structure changes.
Logical data relationships can be created as needed. ADABAS can accommodate any
representational and access requirements dictated by the user environment. Each individual
corporate user can decide how to view data in the system, and can alter data relationships
dynamically—without altering the database or existing programs.
In contrast to systems that require a single model for all data, ADABAS allows you to choose
any structure your application requires. You can access the same data using your choice of
data-model perspective:
􀀀 relational including nested relational (tables within tables)
􀀀 entity relationship, with proven ability to support structural objects
􀀀 hierarchical; network
􀀀 geographical
􀀀 text
Support for an object-oriented data model is currently being developed.
These data models can be combined within a single business solution; multiple solutions can
view ADABAS data using different data models.
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As new requirements develop, ADABAS evolves in both scope and complexity without
redesign of the database or reprogramming of application systems. For example, field and
access keys may be added to an ADABAS file at any time without reloading or reorganizing
the file.
Operating Structure
Figure 1-1 shows the operating structure of the ADABAS system.
User
Program
ADABAS
Nucleus
I/O Buffer
Work Area
Associator
Data
Storage
CPU Memory Disk File
ADABAS
Threads
ADABAS
Utility
TP Monitor
Figure 1-1: The ADABAS System
Nucleus, I/O Buffer, and Threads
The ADABAS nucleus and input/output (I/O) buffer are loaded into main memory at startup.
The “nucleus” is a set of programs that drive ADABAS, coordinate all work, and translate user
program statements into ADABAS commands. All programs access ADABAS files through the
nucleus. All database activities such as data access and update are managed by the ADABAS
nucleus. In most cases, a single nucleus is used to manage a single physical database.
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Note:
For information about running multiple nuclei against a single physical database under a single
operating system image (ADASMP), see page 82; or under multiple MVS/ESA images
(ADAPLEX+), see page 84.
The ADABAS “I/O” buffer area, which can be resized for each ADABAS session, contains the
most frequently used data and data relationships; it helps to minimize physical input/output
(I/O) activity and thus saves computer time. It contains blocks read from the database and blocks
to be written to the database:
􀀀 For blocks read from the database, a “buffer algorithm” ensures that the most frequently
accessed blocks stay in memory. When a block from the database is needed, the buffer content
is checked to determine if the block is already in memory, thus avoiding unnecessary reads.
􀀀 Multiple updates are accumulated in a block before being written (“flushed”) to external
storage.
ADABAS provides multithreaded processing to maximize throughput. If I/O activity suspends
command processing in an active thread, ADABAS automatically switches to another thread.
The user may set the number of 8-kilobyte threads to be used for an ADABAS session up to a
maximum of 250.
ADABAS
ADABAS
Buffer
Thread1
Thread2
Thread3
..
Threadn
Associator
Data
Storage
Figure 1-2: ADABAS Multithread Processing
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Data Storage, Associator, and Work
The Data Storage, Associator, and Work components are physical disk areas. Data Storage
contains raw data, generally in compressed form. The Associator contains information about
data relationships. The Work area contains the data protection area and temporary storage for
intermediate results in complex search operations. See the chapter ADABAS Design starting
on page 13 for more information about these database components.
Utilities, User Programs, and TP Monitors
Utilities
Database services such as loading or deleting files are handled by an integrated set of online and
batch-mode “utility” programs. Most utilities can be run in parallel with normal database
activity to preclude interruption of daily production.
ADABAS utilities provide initial design and load operations, backup/restore/recovery routines,
database modification routines, and audit/control/tuning procedures. See the Utilities chapter
starting on page 49 for a brief explanation of each utility.
User Programs
The nucleus is called using a batch or online “user program” written in
􀀀 NATURAL, Software AG’s fourth-generation application development environment, or some
other fourth-generation language; or
􀀀 Assembler, or a third-generation programming language such as FORTRAN, COBOL, or PL/I
(the REXX/VSE interpreter language is also supported) that uses the powerful and flexible
ADABAS direct call interface. Each ADABAS call is accompanied by a parameter list
identifying buffers defined in the user program that are used to transfer information to and from
ADABAS.
Note:
See page 100 for information about ADABAS Native SQL, a precompiler for Ada, COBOL,
FORTRAN, and PL/I programs; and page 101 for information about ADABAS SQL Server, an
SQL interface to ADABAS.
Data from VSAM, DL/I, IMS/DB, SESAM, or TOTAL database structures can be transferred
to and stored in ADABAS using ADABAS “bridge” products. The original, unmodified
programs continue operating with their original data access commands while the bridge
products intercept the data access commands and translate them to ADABAS direct calls. See
page 88 for more information about ADABAS bridges.
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Special User Programs: Triggers and Stored Procedures
The ADABAS triggers and stored procedures facility, an integral part of ADABAS, can be used
with NATURAL (see page 102) and ADABAS ONLINE SYSTEM (see page 71) to write and
manage triggers and stored procedures in the ADABAS server environment. “Triggers” are
systematically used programs that are started automatically based on an event; they can be used
to ensure referential integrity, for instance. “Stored procedures” are programs used by a number
of different clients that are executed by ADABAS as a result of a special user call. Storing these
programs in an ADABAS file on the server reduces the amount of data traffic to and from the
server. See page 43 for more information about ADABAS triggers and stored procedures.
TP Monitors, Adalinks, and the ADABAS API
Since most systems do not allow a standard call to ADABAS, Software AG provides an
application program interface (API) to translate calls issued by an application program into a
form that can be handled by ADABAS. The ADABAS API is available across all supported
mainframe platforms for both batch and online operations.
Online operations are controlled by teleprocessing (TP) monitors, which serve as
telecommunication interfaces to ADABAS. Supported TP monitors are listed on page 4.
Software AG provides versions of the ADABAS API that are specific to particular TP monitors.
“Adalink” is a generic term that refers to the portion of the API that is specific to a particular
TP monitor.
Batch applications are supported in both single-user and multiuser mode (see page 11 for a
discussion of these modes). The ADABAS batch API uses a standard calling convention that
is supported by all major programming languages through their CALL mechanisms. Most
mainframe operating systems allow batch application modules to be linked either with the batch
API or with ADAUSER.
Software AG strongly recommends linking batch application programs with the ADABAS
version-independent module ADAUSER. The ADAUSER module can optionally be linked
with the ADABAS API. ADAUSER provides upward compatibility with ADABAS releases
and a degree of isolation from future changes to the API or to mechanisms that handle
interregion communication between the user and the nucleus (see page 12).
A client running under OpenEdition MVS can access ADABAS version 6.2. An OpenEdition
application containing calls to ADABAS can be linked with either the batch API or ADAUSER.
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Executing ADABAS
Session Types
Three types of sessions can be identified for ADABAS:
􀀀 The “ADABAS session” starts when the nucleus is invoked and ends when the nucleus is
terminated. An ADABAS nucleus is invoked using job control specific to a particular operating
system that contains ADABAS start-up or “ADARUN” parameters.
􀀀 A “user” is either a batch mode program or a person using a terminal. A “user session” can occur
only during an ADABAS session; that is, when the ADABAS nucleus is active. A user session
is a sequence of ADABAS calls optionally starting with an open user session (OP) command
and ending with a close user session (CL) command.
􀀀 A “utility session” is executed in batch, or online using the ADABAS ONLINE SYSTEM. Some
utilities require that the ADABAS nucleus be active; others do not. ADARUN start-up
parameters are also used for executing utilities.
Storage Areas
The ADABAS nucleus and each user program or ADABAS utility is executed in a separate
storage area defined by the operating system. The name of the storage area depends on the
operating system:
BS2000 task
MVS address space, data space, Hiperspace
VM virtual machine
VSE partition, address space, data space
For consistency and simplification, ADABAS manuals refers to all non-VM areas (task, address
space, partition, etc.) as “regions”. VM areas are called “virtual machines”.
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Modes of Operation
ADABAS supports two modes of operation: single-user and multiuser.
Single-user mode is in effect when a user program (or ADABAS utility) is executed in the same
partition/region as the ADABAS nucleus.
ADABAS
ADABAS
Buffer
Thread1
User Program
(or ADABAS utility)
Region /
Partition
Associator
Data
Storage
Figure 1-3: Single-User Mode
Multiuser mode is in effect when the ADABAS nucleus is located in a separate partition/region.
It is the most efficient and therefore the recommended mode of operation.
ADABAS
ADABAS
Buffer
Thread1
Thread2
..
Threadn
User Program 1
User Program 2
ADABAS Utility
User Program 3
Associator
Data
Storage
Figure 1-4: Multiuser Mode
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When using ADABAS in multiuser mode, interregion communication is handled by ADABAS
in a manner that takes optimum advantage of the communications facilities offered by the
various operating systems.
For single-user mode, the appropriate ADABAS nucleus JCL must be included with the job
control for the utility or user program.
ADARUN Start-up Parameters
The ADARUN control statement defines and starts the ADABAS operating environment. The
ADARUN control statement also starts ADABAS utilities. ADARUN
􀀀 loads the ADAIOR module, which performs all database I/O and other
operating-system-dependent functions;
􀀀 interprets the ADARUN parameter statements; then loads and modifies the appropriate
ADABAS nucleus or utility modules according to the ADARUN parameter settings; and
􀀀 transfers control to ADABAS.
The ADARUN statement, normally a series of entries each specifying one or more ADARUN
parameter settings, is specified in the DDCARD (MVS/ESA, VM/ESA, or BS2000) or VSE
CARD dataset.
Session Control
ADABAS provides several ways to monitor and control ADABAS, user, and utility sessions:
􀀀 ADABAS “operator commands” can be entered from the operator console during an ADABAS
session or during utility operation.
􀀀 The ADADBS OPERCOM utility function can issue operator commands to the ADABAS
nucleus. ADABAS then issues a message to the operator confirming the command execution.
􀀀 For those using ADABAS ONLINE SYSTEM, functions corresponding to operator commands
can be executed while an ADABAS session is active using menu options or direct commands.
Operator commands can be used to terminate an ADABAS or user session; display nucleus or
utility information; log commands; and change ADABAS operating parameters or conditions.
ADABAS “direct call commands” can also be used to open and close a user session. See page
35 for more information about direct call commands.
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