1. Efficient Adabas Access

2. ADABAS Access READ PHYSICAL READ BY ISN (GET) READ LOGICAL FIND
* Select the correct access method.
* Code it efficiently.
READ PHYSICAL
READ BY ISN (GET)
READ LOGICAL
FIND
HISTOGRAM

3. Natural Commands READ Physical Data Storage
Use when reading more than 20% of the records in a file
Generally least expensive method to read all records
Only update if
Potential double updates will not be a problem
Restartability not a problem
Safest to run when file not being updated

4. ADABAS Access - READ PHYSICAL
Access to Data Storage only.
Records returned in the order they are stored physically in Data Storage
* Can results in 4 I/Os (1 per block) & 14 ADABAS Calls
* Order of records returned: 2,1,14,3,5,12,4,6,7,8,11,9,20,21

5. Natural Commands READ by ISN Address Converter Data Storage
Use when reading more than 20% and some updating
ISN use ensures no double updates & no missed updates
ISN may be used as restart point
Second fastest access method
Used when updating file but not one for one with the outside loop

6. ADABAS Access - READ BY ISN
Access to Address Converter & Data Storage
Records returned in ascending ISN order

7. Natural Commands READ Logical Inverted List Address Converter1
Inverted List 4
Data Storage
Address Converter 2 3
Use when reading 1 record or a small range of records
Returned in sorted order by index read
Be careful when updating read key fields

8. ADABAS Access - READ LOGICAL
Returns records in sequence by Descriptor, Sub-, or Super-Descriptor
Accesses Inverted List, Address Converter, and Data Storage
Useful for reading small portion of a file
Consistent performance

9. ADABAS Access - READ LOGICAL
* Access inverted list for ADAMS
* Access Address Converter and pick up second entry (RABN of ISN 2)
* Access block 125 of data storage.
* Move across block to record with ISN 2 (first in block)
* Access Address Converter and pick up seventh entry (RABN of ISN 7)
* Access block 127 of data storage
* Move across block to record with ISN 7 (3rd record)
* Repeat Address Converter/data storage access for records with ISNs 9 and 12
* Access Inverted List for Baker.
* Access Address Converter and pick up 1st entry (RABN of ISN 1)
* Continue as above for remaining BAKERs, CHARLES, DAVENPORT and DAVIS.

10. Natural Commands FIND Memory Inverted List Work Address Converter2
Data Storage 3

11. Natural Commands Returns records in *ISN sequence
FIND
Useful for accessing small groups of records with one or more selection criteria
Returns records in *ISN sequence
A FIND which selects a set of records > 51 will generate I/O to work part 3
Complex FINDs can generate I/O to work part 2

12. Natural Commands LAST-NAME = ‘BROWN’
FIND
Simple find (algorithm 1):
LAST-NAME = ‘BROWN’
Moderate complexity (algorithm 2):
LAST-NAME = ‘BROWN’ OR ‘JONES’
Complex FIND (algorithm 4):
FIND PERSONNEL WITH AGE > #AGE AND SEX = #SEX AND VET-STATUS = ‘V’

13. ADABAS Access - FIND
Selects a set of records & returns that set in ISN sequence
Access Inverted List & select set of records which meet search criteria
If number of ISNs > 51, ADABAS uses Work DS
Access Address Converter to obtain DS RABN

14. ADABAS Access - FIND Read block from Data Storage & locate record
Repeat for each ISN in the list
FIND SORTED BY - avoid when possible
Non descriptor search criteria - ensure it is not primary criteria

15. ADABAS Access - FIND
FIND PERSONNEL WITH NAME = ‘ADAMS’

16. ADABAS Access - FIND FIND PERSONNEL WITH NAME = ‘ADAMS’
Access Inverted List for value ADAMS.
Results in ISN list of 2, 7, 9, 12

17. ADABAS Access - FIND FIND PERSONNEL WITH NAME = ‘ADAMS’
Access Address Converter to obtain RABN.

18. ADABAS Access - FIND FIND PERSONNEL WITH NAME = ‘ADAMS’
Access Data Storage to retrieve record.

19. ADABAS Access - FIND
FIND IN PERSONNEL WITH LAST-NAME = ‘ADAMS’ THRU ‘DAVIS’
Access Inverted List for ‘ADAMS’, ‘BAKER’, ‘CHARLES’, ‘DAVENPORT’, and ‘DAVIS’
Form ISN list: 1,2,3,4,5,6,7,8,9,11,12,14,20,21. This merging is additional work not required by READ LOGICAL.
Access Address Converter and Data Storage.
Records NOT returned in name order!

20. ADABAS Access - FIND
Should only be used if no work file I/O is involved (<51 records).
Useful for multiple, non-contiguous values of descriptor (NAME = ‘SMITH’ OR = ‘CARROLL’ OR = ‘JONES’).
Trade offs between READ logical and FIND.

21. Natural Commands HISTOGRAM Inverted List
Use when only descriptor, sub-descriptor or super descriptor components needed
Use for validation of data

22. ADABAS Access - HISTOGRAM
Only has Access to the Inverted Lists.
Returns two items:
Value of descriptor
Number of records which have that value
ISNs are NOT returned to Natural even though they’re in the inverted lists.
1. Returns value of ‘F’ and *NUMBER = 234

23. ADABAS Access - HISTOGRAM
Beginning and Ending Values Usually Specified.
Efficient way to determine if a particular value exists for a descriptor.
Efficient way to determine how many records have a particular value for a descriptor.
If all data for requirements is available in Inverted List - Use HISTOGRAM or FIND NUMBER

24. Direct Calls How records are accessed by ADABAS
Direct Call Action Performed
L READ by ISN
L READ physical
L READ logical
L9 HISTOGRAM

25. Direct Calls How records are accessed by ADABAS
Direct Call Action Performed
L READ by ISN w/ hold
L READ physical w/ hold
L READ logical w/ hold

26. Direct Calls How records are accessed by ADABAS
Direct Call Action Performed
S FIND
S FIND w/ hold
A1/A4 UPDATE
N1/N4 STORE
E1/E4 DELETE

27. ADABAS Access - SUMMARY
GET - Reread Record
HISTOGRAM - All required data available in Inverted List
READ PHYSICAL - More than 20% of file and no updates
READ BY ISN - More than 20% of file and updates
FIND - Multiple, non-contiguous values of descriptor; Small set of records; sequence not important
READ LOGICAL - Most others

28. Natural 4 and Adabas
Dynamic change of reading direction within an active READ or HISTOGRAM processing loop.
Dynamic repositioning within a READ processing loop.
New comparators LESS/GREATER THAN and LESS/GREATER EQUAL for READ and HISTOGRAM statements.
Support of Multi-Fetch in FIND, HISTOGRAM and READ statements.
New keyword TO that enables end of range condition (ENDING AT) to be controlled by the database itself.
Support of the Adabas Transaction Manager.

29. Questions ?