Adabas Training

All About Adabas

jonathan.j.martin@eds.com

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Course Scope

Strengths of Adabas Inside Adabas Using Adabas Conclusion

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ADABAS - Strengths

Compression of DATA Performance Fault Tolerance High Availability

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ADABAS - Strengths

Compression of DATA– Why Data is compressed?

Saves lot of SpaceMany ADABAS files require only 50% to 60% of the space used for the raw data.Even with the addition of approximately 25% for the access structures stored in the Associator, ADABAS storage requirements are still less than those required for other DBMS

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ADABAS - Strengths

Compression of DATA– ADABAS records are internally stored in

compressed format.– ADABAS defines and executes compression at

field level.– During retrieval of data, ADABAS decompresses

the data.

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ADABAS - Strengths

Compression of DATAThere are 3 TYPES of compression1. Default Compression( also called Normal

Compression)

2. Null Suppression

3. Fixed Format

We can choose the type of compression for a field by setting the compression option in the file definition.

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ADABAS - Strengths

Compression of DATA

DB 252 File 3 - AUTOMOBILEST L DB Name F Leng S D Remarks- - ------------------------------ - ---- - - ----------- 1 AA COLOR A 3 N D 1 AB MAKE A 20 N D 1 AC MODEL A 20 N 1 AD LICENSE A 15 N 1 BA YEAR N 4.0 N 1 BB HORSEPOWER N 3.0 N 1 BC PRICE N 5.0 N 1 BD RECALLS N 5.0 N 1 S1 SP-MAKE-MODEL A 40 N S

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ADABAS - Strengths

Compression of DATA1. Default Compression:

Compresses the trailing blanks and leading zeroes.

An empty field is replaced by one-byte Empty Field Counter (EFC)

At the beginning of each field there is an one-byte field called Inclusive Length Byte (ILB) which stores the length of each fields (including one byte for ILB)

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ADABAS - Strengths

Compression of DATA– Example for Default Compression

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ADABAS - Strengths

Compression of DATA 2. Null Suppression : similar to Default Suppression BUT doesn’t allow zeros or blanks for Descriptor

defined with Null Suppression3. Fixed Format: no compression at all Doesn’t need one byte length indicator (ILB) Mostly used for one-byte fields.

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ADABAS - Strengths

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.

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ADABAS - Strengths

Fault Tolerance– ADABAS recovers automatically after an

abnormal database or system termination.– If a transaction was interrupted, ADABAS

automatically resets all changes of the uncompleted transaction so that the database is consistent.

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ADABAS - Strengths

High Availability– ADABAS is designed for operation 7 days a week

and 24 hours a day.– files can be loaded and unloaded, backed up and

restored, and system performance can be analyzed without interrupting the active database.

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Course Scope

Strengths of Adabas Inside Adabas Using Adabas Conclusion

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Inside ADABAS

ADABAS System

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Inside ADABAS

Overview of Adabas and Front-ends

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Inside ADABAS

Data Storage

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Inside ADABAS

Associators – Inverted List & Address converters

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Inside ADABAS

Adabas access technique

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Inside ADABAS

Example

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Inside ADABAS

Example

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Inside ADABAS

LogsPLOG – Protection Log

– records before- and after-images of records and other elements when changes are made to the database.

CLOG – Command Log– records each ADABAS command that is issued.

RLOG – Recovery Log– records additional info that the ADABAS Recovery Aid can

use for recovery

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Inside ADABAS

FDT – Field Definition Table

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Inside ADABAS

FDT Field options

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Inside ADABAS

ADABAS field types –> 4 field types

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Inside ADABAS

How ADABAS finds the data…

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Course Scope

Strengths of Adabas Inside AdabasUsing Adabas Conclusion

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Using ADABAS

READ Command FIND Command GET Command HISTOGRAM Command STORE UPDATE DELETE

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Using ADABAS

READ Command - 3 TYPES1. READ LOGICAL (READ BY)

2. READ BY ISN

3. READ PHYSICAL

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Using ADABAS

READ LOGICAL (READ BY) Following are the steps to process logical READ

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Using ADABAS

READ LOGICAL – Diagrammatic view

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Using ADABAS

READ BY ISN

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Using ADABAS

READ BY ISN - Diagrammatic View

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Using ADABAS

READ PHYSICAL

1. In Processing a physical READ, ADABAS goes directly to Data Storage and reads the records as they sit in the storage.

2. It does not goes thru an Inverted List

3. It does not goes thru the address converter

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Using ADABAS

READ PHYSICAL – Diagrammatic View

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Using ADABAS

FIND command1. When FIND command is issued, it first

builds an inverted list from the existing inverted list.

2. It stores the inverted list in the Work Area.3. From the newly built Inverted list, it

accesses the data storage thru the address converter.

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Using ADABAS

FIND command – Diagrammatic view

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Using ADABAS

GET command– Used to retrieve single record using the ISN.– But the Problem is that we have to know the ISN.– So Mostly we use GET when we need to access

a record which has been accessed shortly before.– So, When we access it for the first time, we store

the ISN. – Then when we need it again, we can use the ISN

and issue the GET command.

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Using ADABAS

GET command – Diagrammatic View

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Using ADABAS

HISTOGRAM Command

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Using ADABAS

HISTOGRAM Command

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Using ADABAS

HISTOGRAM – Diagrammatic View

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Using ADABAS

So far, we have seen ways to extract data from the ADABAS.

Now, we are going to see , how we are going to put data into the ADABAS.

For that, we use:1. STORE ( similar to INSERT in SQL)

2. UPDATE and

3. DELETE ( this one for removing data)

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Using ADABAS

STORE command

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Using ADABAS

UPDATE Command To update an Adabas record:

1. retrieve the Adabas record

2. ADABAS will “HOLD” the record, when it sees that we are retrieving for UPDATE

3. No other program can have access to the “HOLD” record, until it is released by the UPDATE.

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Using ADABAS

UPDATE Command

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Using ADABAS

DELETE Command

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Using ADABAS

DELETE Command - Example

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ADABAS to NATURAL Cross-reference

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ADABAS to NATURAL Cross-reference

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Course Scope

Strengths of Adabas Inside Adabas Using AdabasConclusion

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ADABAS - Q & A

Got any Questions?

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Helps Available

Following are the types of help available when are dealing with Natural-Adabas.

1. Issue HELP command on editor line

2. Issue ? on editor line

3. or mail me -> jonathan.j.martin@eds.com

T H A N K Y O U !!!