Mapping Adabas Fields That Have Special Characteristics

In a Master File, you can describe certain types of fields that affect retrieval strategy or optimization.

Use of Master File Fields With ISN Support

Reference:

ISN for Insert

The Adapter for Adabas can employ a data retrieval strategy through Read Logical by ISN (L1) calls. It can be used to determine the Internal Sequence Number (ISN) of a record that was read or that will be inserted into an Adabas file.

ISN-based access is applicable only if an ISN field is described in the Master File. This field has a field name that is user-defined and an ALIAS of ISN. The Usage format is I and the Actual format must be I4. This field can be defined only in segments that contain non-repeating data (that is, using an access method defined in the Access File as ADBS):

FIELD=ISN_FIELD, ALIAS=ISN, I10, I4, $

Equality tests on the ISN field can be used to retrieve a single record when the:

Report request contains an equality operator in the selection test on an ISN list.
or
ISN field is used as the cross-referenced field in the Join to an Adabas file.

Adabas returns the Response Code 113 if the record with the ISN defined in the test is not present in the Address Converter for the file. The adapter returns the following message: "Record is not found".

The Adapter for Adabas uses Read Logical by ISN (L1) calls to retrieve all records for the entry segment when the:

Report request does not contain optimizable selection criteria on an inverted list.
Access File contains a SEQFIELD value for the segment whose value is equal to the ISN field name.

For example, the Access File ADATEST contains:

SEGNAM=S01, ACCESS=ADBS , ... ,SEQFIELD=ISN_FIELD ,$

Adabas returns each record in ascending order by the value of the ISN.

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Example: Equality Test on ISN Field

TABLE FILE ADATEST
PRINT AA_FIELD AJ_FIELD
WHERE ISN_FIELD EQ 1100
END

Note: Multifetch option will be suppressed for this call.

Read Logical by ISN (L1) calls to retrieve a subset of records for the entry segment when the:

Report request contains the GE/GT relational operator in the selection test on an ISN list.
Report request does not contain any selection tests on an inverted list.
Access File contains a SEQFIELD value for that segment.

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Example: Inequality Test on ISN Field

Access File ADATEST contains:

SEGNAM=S01, ACCESS=ADBS, ... ,SEQFIELD=AA_FIELD ,$

Read Logical by ISN (L1) is used:

TABLE FILE ADATEST
PRINT AA_FIELD AE_FIELD
WHERE ISN_FIELD GT 1100
END

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Reference: ISN for Insert

After issuing an Insert request on a file with an ISN field in the Master File, the resulting ISN generated by Adabas is displayed by the message FOC4592:

(FOC4592) RECORD IS INSERTED WITH ISN : nnnnn

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Example: Issuing an Insert Request

MODIFY FILE ADBTEST
FREEFORM AA_FIELD AJ_FIELD
MATCH AA_FIELD AJ_FIELD
ON NOMATCH INCLUDE
ON MATCH REJECT
DATA
11111111, TAMPA
END

ADBTEST ADBSINX ON 09/20/2002 AT 15.22.16
(FOC4592) RECORD IS INSERTED WITH ISN : 11
(FOC4566) RECORDS AFFECTED DURING CURRENT REQUEST : 1/INSERT

TRANSACTIONS: TOTAL = 1 ACCEPTED= 1 REJECTED= 0
SEGMENTS: INPUT = 1 UPDATED = 0 DELETED = 0

You can assign a value for the ISN field if the Insert request contains the ISN field and the assigned value is not 0.

The adapter will issue an Adabas N2 Direct Call to assign this ISN value to the inserted record. Adabas returns Response Code 113 if this value was already assigned to another record in the file or if it is larger than the MAXISN in effect for the file.

Master File Fields and GFBID Support

Reference:

Using the GFBID Parameter

The Adapter for Adabas can optimize the performance of queries that use the same Adabas field lists repeatedly. Field lists are generated in Adabas format buffers, and can be retained.

Global Format Buffer ID (GFBID) support is applicable only if a GFBID field is present in the Master File. This field has a user-defined field name, and an ALIAS of GFBID. This field is used to determine the Global Format Buffer ID that will be defined in read requests with identical field lists for the same database. The GFBID field has a USAGE format of A8 and an ACTUAL format of A8. This field can be defined only in segments that contain non-repeating data (that is, the access method defined in the Access File is ADBS).

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Example: Using GFBID Syntax in a Master File

FIELD=GID_FIELD, ALIAS=GFBID, A8, A8, $

Note:

If the field list is changed but the same GFBID is used in a request, then incorrect results may be displayed. In some cases, a message about the possible mismatch between the Field Definition Table (FDT) and Master File will be issued.
If two requests have the same list of selected fields but different fields are used in selection criteria, then the requests must use different GFBID values.

The GFBID field can be defined in the Master File manually.

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Reference: Using the GFBID Parameter

The value of GFBID can have up to 8 bytes and must start with a digit or uppercase character.

If GFBID is used in a request against a file that contains simple PE/MU segments, it will be applied to Adabas calls to get the field values from these segments. The GFBID value will be adjusted for each non-ADBS segment, that is, a segment number will be placed in the last (8th) byte of the GFBID field.

Calls to a PE (periodic element) with MU (multi-value) child or an MU with PE parent segment will not use GFBID values.

Note: To make the GFBID value unique within Adabas, do not use 8 byte GFBID values for these types of calls.

If a GFBID field is defined in the Master File, it can be used in a request as part of the selection test. The adapter will take the GFBID value from the selection criteria, deactivate the field, and remove it from the match array. The GFBID value is placed in the ADD5 field of the Adabas Control Block for the request.
If the GFBID is applied to an Adabas call, then field name ADD5 appears in the adapter trace. GFBID values that were issued in all requests to the database are accumulated in the Adabas internal queue. These values can be removed from the queue by issuing the following adapter SET command:
```
ENGINE ADBSINX SET GFBID_OFF {ALL|value} DBID number
```

When a single value is specified in the SET command, all values issued for child segments are removed as well. If value contains blanks, value must be enclosed in single quotation marks.

ALL clears all GFBID values.

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Example: Using GFBID Syntax

Master File ADATEST contains:

FIELD=GID_FIELD, ALIAS=GFBID, A8, A8, $

Request 1. Global ID = ABC1:

TABLE FILE EMPFILE
PRINT AA_FIELD AJ_FIELD ISN_FIELD AQ0201_OCC AR_FIELD AS_FIELD, 
AT_FIELD
WHERE ISN_FIELD GT 1100 AND GID_FIELD EQ 'ABC1';
END

Result:

PAGE 1
 
 AA_FIELD AJ_FIELD     ISN_FIELD AQ0201_OCC AR_FIELD AS_FIELD AT_FIELD
 -------- --------     --------- ---------- -------- -------- --------
 30034517 DERBY        1105      1          UKL      6500     750
 30034517 DERBY        1105      2          UKL      6800     1240
 30034517 DERBY        1105      3          UKL      7100     1345
 30034517 DERBY        1105      4          UKL      7450     1450
 30034517 DERBY        1105      5          UKL      7800     1700
 50005600 VIENNE       1106      1          FRA      165810   10000
 50005300 PARIS        1107      1          FRA      166900   5400
 
 NUMBER OF RECORDS IN TABLE= 7 LINES= 7

Request 2. Global ID = ABC1, but field's list is changed:

TABLE FILE EMPFILE
PRINT AA_FIELD ISN_FIELD AQ0201_OCC AR_FIELD AS_FIELD AT_FIELD
WHERE ISN_FIELD GT 1100 AND GID_FIELD EQ 'ABC1';
END

Result:

(FOC4567) POSSIBLE MISMATCH BETWEEN FDT AND MFD : file=19879548
(FOC4591) ERROR RETURN ON READ BY ISN : S01 /999:ffffffcd001d00
 
 NUMBER OF RECORDS IN TABLE= 0 LINES= 0

Request 3. Remove value 'ABC1' from Adabas:

ENGINE ADBSINX SET GFBID_OFF ABC1 DBID 3

Request 4. Repeat request 2.

TABLE FILE EMPFILE
PRINT AA_FIELD ISN_FIELD AQ0201_OCC AR_FIELD AS_FIELD AT_FIELD
WHERE ISN_FIELD GT 1100 AND GID_FIELD EQ 'ABC1';
END

Result:

PAGE 1
 
 AA_FIELD ISN_FIELD AQ0201_OCC AR_FIELD AS_FIELD AT_FIELD
 -------- --------- ---------- -------- -------- --------
 30034517 1105      1          UKL      6500     750
 30034517 1105      2          UKL      6800     1240
 30034517 1105      3          UKL      7100     1345
 30034517 1105      4          UKL      7450     1450
 30034517 1105      5          UKL      7800     1700
 50005600 1106      1          FRA      165810   10000
 50005300 1107      1          FRA      166900   5400
 
 NUMBER OF RECORDS IN TABLE= 7 LINES= 7

Request 5. Remove all GFBID values for Database 3 from Adabas:

ENGINE ADBSINX SET GFBID_OFF ALL DBID 3