This document describes various aspects of accessing data in an Adabas database with Natural.
The following topics are covered:
See also Database Management in Profile Parameters Grouped by Category (Parameter Reference documentation) for an overview of the Natural profile parameters that apply when Natural is used with Adabas.
For Natural to be able to access a database file, a logical definition of the physical database file is required. Such a logical file definition is called a data definition module (DDM).
This section covers the following topics:
The data definition module contains information about the individual fields of the file - information which is relevant for the use of these fields in a Natural program. A DDM constitutes a logical view of a physical database file.
For each physical file of a database, one or more DDMs can be defined. And for each DDM
one or more data views can be defined as described View Definition in the
DEFINE DATA statement
documentation and explained in the section Defining a Database View.
DDMs are defined by the Natural administrator with Predict (or, if Predict is not available, with the corresponding Natural function).
Adabas supports array structures within the database in the form of multiple-value fields and periodic groups.
This section covers the following topics:
A multiple-value field is a field which can have more than one value (up to 65534, depending on the Adabas version and definition of the FDT) within a given record.
Assuming that the above is a record in an EMPLOYEES file, the first field
(Name) is an elementary field, which can contain only one value, namely the name of the
person; whereas the second field (Languages), which contains the languages spoken by the
person, is a multiple-value field, as a person can speak more than one language.
A periodic group is a group of fields (which may be elementary fields and/or multiple-value fields) that may have more than one occurrence (up to 65534, depending on the Adabas version and definition of the field definition table (FDT)) within a given record.
The different values of a multiple-value field are usually called "occurrences"; that is, the number of occurrences is the number of values which the field contains, and a specific occurrence means a specific value. Similarly, in the case of periodic groups, occurrences refer to a group of values.
Assuming that the above is a record in a vehicles file, the first field (Name) is an elementary field which contains the name of a person; Cars is a periodic group which contains the automobiles owned by that person. The periodic group consists of three fields which contain the registration number, make and model of each automobile. Each occurrence of Cars contains the values for one automobile.
To reference one or more occurrences of a multiple-value field or a periodic group, you specify an "index notation" after the field name.
The following examples use the multiple-value field LANGUAGES and the
periodic group CARS from the previous examples.
The various values of the multiple-value field LANGUAGES can be referenced
as follows.
| Example | Explanation |
|---|---|
LANGUAGES (1)
|
References the first value (SPANISH).
|
LANGUAGES (X)
|
The value of the variable X determines the value to be referenced. |
LANGUAGES (1:3)
|
References the first three values (SPANISH,
CATALAN and FRENCH).
|
LANGUAGES (6:10) |
References the sixth to tenth values. |
LANGUAGES (X:Y)
|
The values of the variables X and Y determine the
values to be referenced.
|
The various occurrences of the periodic group CARS can be referenced in
the same manner:
| Example | Explanation |
|---|---|
CARS (1) |
References the first occurrence (B-123ABC/SEAT/IBIZA).
|
CARS (X)
|
The value of the variable X determines the occurrence to be
referenced.
|
CARS (1:2)
|
References the first two occurrences (B-123ABC/SEAT/IBIZA and
B-999XYZ/VW/GOLF).
|
CARS (4:7)
|
References the fourth to seventh occurrences. |
CARS (X:Y)
|
The values of the variables X and Y determine the
occurrences to be referenced.
|
An Adabas array can have up to two dimensions: a multiple-value field within a periodic group.
Assuming that the above is a record in a vehicles file, the first field (Name) is an elementary field which contains the name of a person; Cars is a periodic group, which contains the automobiles owned by that person. This periodic group consists of three fields which contain the registration number, servicing dates and make of each automobile. Within the periodic group Cars, the field Servicing is a multiple-value field, containing the different servicing dates for each automobile.
To reference one or more occurrences of a multiple-value field within a periodic group, you specify a "two-dimensional" index notation after the field name.
The following examples use the multiple-value field SERVICING within the
periodic group CARS from the example above. The various values of the
multiple-value field can be referenced as follows:
| Example | Explanation |
|---|---|
SERVICING (1,1)
|
References the first value of SERVICING in the first
occurrence of CARS (31-05-97).
|
SERVICING (1:5,1)
|
References the first value of SERVICING in the first five
occurrences of CARS.
|
SERVICING (1:5,1:10) |
References the first ten values of SERVICING in the first five
occurrences of CARS.
|
It is sometimes necessary to reference a multiple-value field or a periodic group
without knowing how many values/occurrences exist in a given record. Adabas maintains an
internal count of the number of values in each multiple-value field and the number of
occurrences of each periodic group. This count may be read in a READ statement by specifying
C* immediately before the field name.
The count is returned in format/length N3. See Referencing the Internal Count for a Database Array for further details.
| Example | Explanation |
|---|---|
C*LANGUAGES |
Returns the number of values of the multiple-value field
LANGUAGES.
|
C*CARS |
Returns the number of occurrences of the periodic group
CARS.
|
C*SERVICING (1) |
Returns the number of values of the multiple-value field
SERVICING in the first occurrence of a periodic group (assuming
that SERVICING is a multiple-value field within a periodic
group.)
|
To be able to use database fields in a Natural program, you must specify the fields in a database view.
In the view, you specify the name of the data definition module (see Data Definition Modules - DDMs) from which the fields are to be taken, and the names of the database fields (see Field Definitions) themselves (that is, their long names, not their database-internal short names).
The view may comprise an entire DDM or only a subset of it. The order of the fields in the view need not be the same as in the underlying DDM.
As described in the section Statements for
Database Access, the view name is used in the statements
READ, FIND, HISTOGRAM to determine which database
is to be accessed.
For further information on the complete syntax of the view definition option or on the
definition/redefinition of a group of fields, see View
Definition in the description of the DEFINE DATA
statement in the Statements documentation.
Basically, you have the following options to define a database view:
Inside the Program
You can define a database view inside the program, that is, directly within the
DEFINE DATA statement of
the program.
Outside the Program
You can define a database view outside the program, that is, in a separate object:
either a local data
area (LDA) or a global data area (GDA), with the DEFINE DATA
statement of the program referencing that data area.
To define a database view inside the program
At Level 1, specify the view name as follows:
1 view-name VIEW OF ddm-name
where view-name is the name you choose for
the view, ddm-name is the name of the DDM
from which the fields specified in the view are taken.
At Level 2, specify the names of the database fields from the DDM.
In the illustration below, the name of the view is ABC, and it
comprises the fields NAME, FIRST-NAME and
PERSONNEL-ID from the DDM XYZ.
In the view, the format and length of a database field need not be specified, as these are already defined in the underlying DDM.
Sample Program:
In this example, the view-name is
VIEWEMP, and the ddm-name is
EMPLOYEES, and the names of the database fields taken from the DDM
are NAME, FIRST-NAME and PERSONNEL-ID.
DEFINE DATA LOCAL 1 VIEWEMP VIEW OF EMPLOYEES 2 NAME 2 FIRST-NAME 2 PERSONNEL-ID 1 #VARI-A (A20) 1 #VARI-B (N3.2) 1 #VARI-C (I4) END-DEFINE ...
To define a database view outside the program
In the program, specify:
DEFINE DATA LOCAL
USING <data-area-name>
END-DEFINE
...
where data-area-name is the name you choose
for the local or global data area, for example, LDA39.
In the data area to be referenced:
At Level 1 in the Name column, specify the name you choose for the
view, and in the Miscellaneous column, the name of the DDM from
which the fields specified in the view are taken.
At Level 2, specify the names of the database fields from the DDM.
Example LDA39:
In this example, the view name is VIEWEMP, the DDM name is
EMPLOYEES, and the names of the database fields taken from the
DDM are PERSONNEL-ID, FIRST-NAME and
NAME.
I T L Name F Length Miscellaneous
All -- -------------------------------- - ---------- ------------------------->
V 1 VIEWEMP EMPLOYEES
2 PERSONNEL-ID A 8
2 FIRST-NAME A 20
2 NAME A 20
1 #VARI-A A 20
1 #VARI-B N 3.2
1 #VARI-C I 4
To read data from a database, the following statements are available:
| Statement | Meaning |
|---|---|
READ
|
Select a range of records from a database in a specified sequence. |
FIND
|
Select from a database those records which meet a specified search criterion. |
HISTOGRAM
|
Read only the values of one database field, or determine the number of records which meet a specified search criterion. |
The following topics are covered:
The READ statement is used to
read records from a database. The records can be retrieved from the database
in the order in which they are physically stored in the database (READ IN PHYSICAL
SEQUENCE), or
in the order of Adabas Internal Sequence Numbers (READ BY ISN), or
in the order of the values of a descriptor field (READ IN LOGICAL
SEQUENCE).
In this document, only READ IN LOGICAL SEQUENCE is discussed, as it is
the most frequently used form of the READ statement.
For information on the other two options, please refer to the description of the
READ statement in the
Statements documentation.
The basic syntax of the READ
statement is:
READ
view
IN LOGICAL SEQUENCE BY
descriptor
|
or shorter:
READ
view
LOGICAL BY
descriptor
|
- where
view
|
is the name of a view defined in the DEFINE DATA statement and as explained in
Defining a Database
View.
|
descriptor
|
is the name of a database field defined in that view. The values of this field determine the order in which the records are read from the database. |
If you specify a descriptor, you need not specify the keyword
LOGICAL:
READ
view
BY
descriptor
|
If you do not specify a descriptor, the records will be read in the order of values
of the field defined as default descriptor (under Default Sequence) in
the DDM. However, if you specify no
descriptor, you must specify the keyword
LOGICAL:
READ
view
LOGICAL
|
** Example 'READX01': READ ************************************************************************ DEFINE DATA LOCAL 1 MYVIEW VIEW OF EMPLOYEES 2 NAME 2 PERSONNEL-ID 2 JOB-TITLE END-DEFINE * READ (6) MYVIEW BY NAME DISPLAY NAME PERSONNEL-ID JOB-TITLE END-READ END
Output of Program READX01:
With the READ statement in
this example, records from the EMPLOYEES file are read in alphabetical
order of their last names.
The program will produce the following output, displaying the information of each employee in alphabetical order of the employees' last names.
Page 1 04-11-11 14:15:54
NAME PERSONNEL CURRENT
ID POSITION
-------------------- --------- -------------------------
ABELLAN 60008339 MAQUINISTA
ACHIESON 30000231 DATA BASE ADMINISTRATOR
ADAM 50005800 CHEF DE SERVICE
ADKINSON 20008800 PROGRAMMER
ADKINSON 20009800 DBA
ADKINSON 2001100
If you wanted to read the records to create a report with the employees listed in
sequential order by date of birth, the appropriate READ statement would
be:
READ MYVIEW BY BIRTH
You can only specify a field which is defined as a "descriptor" in the underlying DDM (it can also be a subdescriptor, superdescriptor, hyperdescriptor or phonetic descriptor or a non-descriptor).
As shown in the previous example program, you can limit the number of records to be
read by specifying a number in parentheses after the keyword READ:
READ (6) MYVIEW BY NAME
In that example, the READ statement would read no more than 6
records.
Without the limit notation, the above READ statement would read
all records from the EMPLOYEES file in the order of last names
from A to Z.
The READ statement also allows
you to qualify the selection of records based on the value of a descriptor
field. With an EQUAL
TO/STARTING FROM option in the BY clause, you can specify the
value at which reading should begin. (Instead of using the keyword BY,
you may specify the keyword WITH, which would have the same effect). By
adding a THRU/ENDING
AT option, you can also specify the value in the logical sequence
at which reading should end.
For example, if you wanted a list of those employees in the order of job titles
starting with TRAINEE and continuing on to Z, you would use
one of the following statements:
READ MYVIEW WITH JOB-TITLE = 'TRAINEE' READ MYVIEW WITH JOB-TITLE STARTING FROM 'TRAINEE' READ MYVIEW BY JOB-TITLE = 'TRAINEE' READ MYVIEW BY JOB-TITLE STARTING FROM 'TRAINEE'
Note that the value to the right of the equal sign (=) or STARTING FROM option
must be enclosed in apostrophes. If the value is numeric, this text notation is not required.
The sequence of records to be read can be even more closely specified by adding an
end limit with a THRU/ENDING
AT clause.
To read just the records with the job title TRAINEE, you would
specify:
READ MYVIEW BY JOB-TITLE STARTING FROM 'TRAINEE' THRU 'TRAINEE'
READ MYVIEW WITH JOB-TITLE EQUAL TO 'TRAINEE'
ENDING AT 'TRAINEE'
To read just the records with job titles that begin with A or
B, you would specify:
READ MYVIEW BY JOB-TITLE = 'A' THRU 'C' READ MYVIEW WITH JOB-TITLE STARTING FROM 'A' ENDING AT 'C'
The values are read up to and including the value specified after THRU/ENDING AT. In the
two examples above, all records with job titles that begin with A or
B are read; if there were a job title C, this would also
be read, but not the next higher value CA.
The WHERE clause
may be used to further qualify which records are to be read.
For instance, if you wanted only those employees with job titles starting from
TRAINEE who are paid in US currency, you would specify:
READ MYVIEW WITH JOB-TITLE = 'TRAINEE'
WHERE CURR-CODE = 'USD'
The WHERE clause can also be used with the BY clause as follows:
READ MYVIEW BY NAME
WHERE SALARY = 20000
The WHERE clause differs from the BY clause in two respects:
The field specified in the WHERE clause need not be a
descriptor.
The expression following the WHERE option is a logical
condition.
The following logical operators are possible in a WHERE clause:
EQUAL |
EQ |
= |
NOT EQUAL TO |
NE |
¬= |
LESS THAN |
LT |
< |
LESS THAN OR EQUAL TO |
LE |
<= |
GREATER THAN |
GT |
> |
GREATER THAN OR EQUAL TO |
GE |
>= |
The following program illustrates the use of the STARTING FROM, ENDING
AT and WHERE clauses:
** Example 'READX02': READ (with STARTING, ENDING and WHERE clause)
************************************************************************
DEFINE DATA LOCAL
1 MYVIEW VIEW OF EMPLOYEES
2 NAME
2 JOB-TITLE
2 INCOME (1:2)
3 CURR-CODE
3 SALARY
3 BONUS (1:1)
END-DEFINE
*
READ (3) MYVIEW WITH JOB-TITLE
STARTING FROM 'TRAINEE' ENDING AT 'TRAINEE'
WHERE CURR-CODE (*) = 'USD'
DISPLAY NOTITLE NAME / JOB-TITLE 5X INCOME (1:2)
SKIP 1
END-READ
END
Output of Program READX02:
NAME INCOME
CURRENT
POSITION CURRENCY ANNUAL BONUS
CODE SALARY
------------------------- -------- ---------- ----------
SENKO USD 23000 0
TRAINEE USD 21800 0
BANGART USD 25000 0
TRAINEE USD 23000 0
LINCOLN USD 24000 0
TRAINEE USD 22000 0
See the following example program:
The following topics are covered:
The FIND statement is used to
select from a database those records which meet a specified search criterion.
The basic syntax of the FIND statement is:
FIND RECORDS IN
view
WITH
field = value
|
or shorter:
FIND
view
WITH
field = value
|
- where
view
|
is the name of a view as defined in the DEFINE DATA statement and
as explained in Defining a
Database View.
|
field
|
is the name of a database field as defined in that view. |
You can only specify a field which is defined
as a "descriptor" in the underlying DDM (it can also be a subdescriptor, superdescriptor, hyperdescriptor or
phonetic descriptor).
For the complete syntax, refer to the FIND statement documentation.
In the same way as with the READ statement described above, you can limit
the number of records to be processed by specifying a number in parentheses after the
keyword FIND:
FIND (6) RECORDS IN MYVIEW WITH NAME = 'CLEGG'
In the above example, only the first 6 records that meet the search criterion would be processed.
Without the limit notation, all records that meet the search criterion would be processed.
Note:
If the FIND statement contains a WHERE clause (see below),
records which are rejected as a result of the WHERE clause are
not counted against the limit.
With the WHERE
clause of the FIND statement,
you can specify an additional selection criterion which is evaluated after a
record (selected with the WITH clause) has been read and before any
processing is performed on the record.
** Example 'FINDX01': FIND (with WHERE)
************************************************************************
DEFINE DATA LOCAL
1 MYVIEW VIEW OF EMPLOYEES
2 PERSONNEL-ID
2 NAME
2 JOB-TITLE
2 CITY
END-DEFINE
*
FIND MYVIEW WITH CITY = 'PARIS'
WHERE JOB-TITLE = 'INGENIEUR COMMERCIAL'
DISPLAY NOTITLE CITY JOB-TITLE PERSONNEL-ID NAME
END-FIND
END
Note:
In this example only those records which meet the criteria of the
WITH clause and the WHERE clause are processed in
the DISPLAY
statement.
Output of Program FINDX01:
CITY CURRENT PERSONNEL NAME
POSITION ID
-------------------- ------------------------- --------- --------------------
PARIS INGENIEUR COMMERCIAL 50007300 CAHN
PARIS INGENIEUR COMMERCIAL 50006500 MAZUY
PARIS INGENIEUR COMMERCIAL 50004700 FAURIE
PARIS INGENIEUR COMMERCIAL 50004400 VALLY
PARIS INGENIEUR COMMERCIAL 50002800 BRETON
PARIS INGENIEUR COMMERCIAL 50001000 GIGLEUX
PARIS INGENIEUR COMMERCIAL 50000400 KORAB-BRZOZOWSKI
If no records are found that meet the search criteria specified in the WITH and WHERE clauses, the
statements within the FIND processing loop are not executed (for the
previous example, this would mean that the DISPLAY statement would not be executed and consequently
no employee data would be displayed).
However, the FIND statement also provides an IF NO RECORDS
FOUND clause, which allows you to specify processing you wish to
be performed in the case that no records meet the search criteria.
** Example 'FINDX02': FIND (with IF NO RECORDS FOUND)
************************************************************************
DEFINE DATA LOCAL
1 MYVIEW VIEW OF EMPLOYEES
2 NAME
2 FIRST-NAME
END-DEFINE
*
FIND MYVIEW WITH NAME = 'BLACKSMITH'
IF NO RECORDS FOUND
WRITE 'NO PERSON FOUND.'
END-NOREC
DISPLAY NAME FIRST-NAME
END-FIND
END
The above program selects all records in which the field NAME contains
the value BLACKSMITH. For each selected record, the name and first name
are displayed. If no record with NAME = 'BLACKSMITH' is found on the
file, the WRITE statement
within the IF NO
RECORDS FOUND clause is executed.
Output of Program FINDX02:
Page 1 04-11-11 14:15:54
NAME FIRST-NAME
-------------------- --------------------
NO PERSON FOUND.
See the following example programs:
The following topics are covered:
The HISTOGRAM statement is
used to either read only the values of one database field, or determine the number of
records which meet a specified search criterion.
The HISTOGRAM statement does not provide access to any database fields
other than the one specified in the HISTOGRAM statement.
The basic syntax of the HISTOGRAM statement is:
HISTOGRAM VALUE IN
view
FOR
field
|
or shorter:
HISTOGRAM
view
FOR
field
|
- where
view
|
is the name of a view as defined in the DEFINE DATA statement and
as explained in Defining a
Database View.
|
field
|
is the name of a database field as defined in that view. |
For the complete syntax, refer to the HISTOGRAM statement documentation.
In the same way as with the READ
statement, you can limit the number of values to be read by specifying a number in
parentheses after the keyword HISTOGRAM:
HISTOGRAM (6) MYVIEW FOR NAME
In the above example, only the first 6 values of the field NAME would be
read.
Without the limit notation, all values would be read.
Like the READ
statement, the HISTOGRAM statement also provides a STARTING FROM clause
and an ENDING AT (or THRU) clause to narrow down the range
of values to be read by specifying a starting value and ending value.
HISTOGRAM MYVIEW FOR NAME STARTING from 'BOUCHARD' HISTOGRAM MYVIEW FOR NAME STARTING from 'BOUCHARD' ENDING AT 'LANIER' HISTOGRAM MYVIEW FOR NAME from 'BLOOM' THRU 'ROESER'
The HISTOGRAM statement
also provides a WHERE clause which may be used to specify an additional
selection criterion that is evaluated after a value has been read and
before any processing is performed on the value. The field specified in the
WHERE clause must be the same as in the main clause of the
HISTOGRAM statement.
** Example 'HISTOX01': HISTOGRAM ************************************************************************ DEFINE DATA LOCAL 1 MYVIEW VIEW OF EMPLOYEES 2 CITY END-DEFINE * LIMIT 8 HISTOGRAM MYVIEW CITY STARTING FROM 'M' DISPLAY NOTITLE CITY 'NUMBER OF/PERSONS' *NUMBER *COUNTER END-HISTOGRAM END
In this program, the system variables *NUMBER and *COUNTER are
also evaluated by the HISTOGRAM statement, and output with the DISPLAY statement.
*NUMBER contains the number of database records that
contain the last value read; *COUNTER contains the total
number of values which have been read.
Output of Program HISTOX01:
CITY NUMBER OF CNT
PERSONS
-------------------- ----------- -----------
MADISON 3 1
MADRID 41 2
MAILLY LE CAMP 1 3
MAMERS 1 4
MANSFIELD 4 5
MARSEILLE 2 6
MATLOCK 1 7
MELBOURNE 2 8
The MULTI-FETCH clause supports the multi-fetch record retrieval
functionality for Adabas databases.
The multi-fetch functionality described in this section is only supported for Adabas. For information on the multi-fetch record retrieval functionality for Db2 databases, see Multiple Row Processing in the Natural for Db2 part of the Database Management System Interfaces documentation.
The following topics are covered:
In standard mode, Natural does not read multiple records with a single database call; it always operates in a one-record-per-fetch mode. This kind of operation is solid and stable, but can take some time if a large number of database records are being processed.
To improve the performance of those programs, you can use the MULTI-FETCH
clause in the FIND, READ or HISTOGRAM
statements. This allows you to define the multi-fetch factor, a numeric value that
specifies the number of records read per database access.
|
|
FIND
|
|
|
MULTI-FETCH
|
|
ON
|
|
|
READ
|
OFF
|
|||||||
HISTOGRAM
|
OF
multi-fetch-factor
|
Where the multi-fetch-factor is:
a numeric constant in the value range (0-2147483647).
a variable in integer, binary (B1-B4), or packed/numeric with only integer digits format.
At statement execution time, the runtime checks if a multi-fetch-factor greater than 1 is supplied for the database statement.
If the multi-fetch-factor is:
| a negative value | a runtime error is raised. |
| 0 or 1 | the database call is continued in the usual one-record-per-access mode. |
| 2 or greater | the database call is prepared dynamically to read multiple
records (for example, 10) with a single database access into an auxiliary buffer
(multi-fetch buffer). If successful, the first record is transferred into the
underlying data view. Upon the execution of the next loop, the data view is
filled directly from the multi-fetch buffer, without database access. After all
records have been fetched from the multi-fetch buffer, the next loop results in
the next record set being read from the database. If the database loop is
terminated (either by end-of-records, ESCAPE, STOP, etc.), the content of the multi-fetch buffer
is released.
|
A multi-fetch access is only supported for a browse loop; in other words, when the records are read with "no hold".
The program does not receive "fresh" records from the database for every loop, but operates with images retrieved at the most recent multi-fetch access.
If a loop repositioning is triggered for a READ / HISTOGRAM statement, the content of the multi-fetch
buffer at that point is released.
The multi-fetch feature is not possible and leads to a corresponding syntax error at compilation,
The first record of a FIND
loop is retrieved with the initial S1 command. Since Adabas multi-fetch
is just defined for all kinds of Lx commands, it first can be used from
the second record.
The size occupied by a database loop in the multi-fetch buffer is determined according to the rule:
| ((record-length + isn-entry-length) * multi-fetch-factor ) + 4 + header-length |
| = |
| ((size-of-view-fields + 20) * multi-fetch-factor) + 4 + 128 |
The multi-fetch factor is automatically reduced at runtime if
the number of records to be read (e.g. READ (2) ..) is less than the multi-fetch factor,
but only if no WHERE clause is involved;
the number of records selected (*NUMBER in FIND statement) is less than the multi-fetch
factor;
the size of the multi-fetch buffer is not sufficient to receive the number of records requested by the multi-fetch factor;
Moreover, the multi-fetch option is completely ignored at runtime if
the multi-fetch factor contains a value less than or equal to 1;
the multi-fetch buffer is not available or does not have enough free space (for more details, refer to Size of the Multi-Fetch Buffer below.
The statement executed is READ MULTI-FETCH 100 EMPL-VIEW BY
NAME.
The record size (length of the fields in the EMPL-VIEW view) is
1000 bytes; the multi-fetch buffer (MULFETCH) size is 64 KB.
At runtime, the multi-fetch factor 100 is automatically reduced to 64 to
arrange that the total record buffer fits into the MULFETCH buffer.
In order to control the amount of storage available for multi-fetch purposes, you can
limit the maximum size of the Natural multi-fetch buffer (MULFETCH).
In the Natural
parameter module (described in the Operations
documentation), you can specify a static assignment via the parameter macro NTDS:
NTDS MULFETCH,nn
At session start, you can also use the profile parameter DS:
DS=(MULFETCH,nn)
where nn represents the complete size allowed
to be allocated for multi-fetch purposes (in KB). The value may be set in the range
(0 - 1024), with a default value of 64. Setting a high value does not
necessarily mean having a buffer allocated of that size, since the multi-fetch handler
makes dynamic allocations and resizes, depending on what is really needed to execute a
multi-fetch database call. If no multi-fetch database call is executed in a Natural
session, the multi-fetch buffer will never be created, regardless of which value was
set.
If the value 0 is specified, the multi-fetch processing is completely
disabled, no matter if a database access statement contains a MULTI-FETCH OF
... clause or not. This allows to completely switch off all multi-fetch
activities when there is not enough storage available in the current environment or for
debugging purposes.
The execution of a multi-fetch call requires an intermediate user buffer area in
Adabas. The size of this buffer is set with the Adabas LU
parameter, with a default value of 65535 (64 KB). If the size of the Adabas
LU parameter is less than the size of the Natural
MULFETCH buffer, Natural runtime error NAT3152 (Internal
user buffer too small.) can occur during multi-fetch processing,
indicating insufficient user buffer space.
You can avoid such errors by setting the size of the MULFETCH buffer
(default is 64 KB) to the same value or less than the Adabas intermediate buffer
size (default is 64 KB, set with the Adabas LU parameter).
This implies that if you increase the MULFETCH buffer, you must
increase the Adabas intermediate user buffer accordingly. Example: set
LU=102400 (100 KB) if DS=(MULFETCH,100).
The Natural MULFETCH buffer has an unused reserve space of 6 KB. This
prevents Natural NAT3152 runtime errors that can occur if the Adabas
LU parameter is set to 64 KB (default) or higher, and is
the same as or larger than the MULFETCH buffer.
A multi-fetch call is usually executed in the ACB (Adabas control block) layout.
However, a multi-fetch call is executed in the ACBX (extended Adabas control block) layout if all of the following are true:
The Natural profile parameter ADAACBX is set to ON.
The total record buffer size (= single record size * multi-fetch factor) of the multi-fetch call is larger than 32 KB.
The Natural DB profile parameter is set to Adabas
Version 8 (or above) for the database accessed when the program is
cataloged.
The Natural MULFETCH buffer is larger than 32 KB (default is 64
KB).
For more information about the syntax of the MULTI-FETCH clause in the
supported statements, see FIND, READ or HISTOGRAM.
You can use the MULTI-FETCH clause to improve the performance of the
supported statements by defining the number of records read per database access as a
numeric value called the multi-fetch factor.
|
|
|
|
|
MULTI-FETCH |
|
|
|
|
Valid values of the multi-fetch-factor are:
Based on the value of the multi-fetch-factor specified in the database statement, the database call is processed as follows:
| Value | Database call process description |
|---|---|
| Negative | A negative value is out of range and results in a run-time error. |
| 0 or 1 | A value of 0 or 1 indicates to process one record per database access (which is the standard processing mode). |
| 2 or greater | A value of 2 or greater indicates that the database call is dynamically
prepared to read multiple records with a single database access and store them in
the multi-fetch buffer. If successful, the first record is transferred to the
underlying data view. In the next loop, the data view is filled directly from the
multi-fetch buffer, without accessing the database. After fetching all records
stored in the multi-fetch buffer, the database call reads the next set of records
from the database. If the database loop is terminated by an action, such as
end-of-records, ESCAPE,
or STOP, the content of the
multi-fetch buffer is released.
|
This section discusses processing loops required to process data that have been
selected from a database as a result of a FIND, READ or
HISTOGRAM statement.
The following topics are covered:
Natural automatically creates the necessary processing loops which are required to
process data that have been selected from a database as a result of a FIND, READ or HISTOGRAM statement.
In the following example, the FIND loop selects all records from the EMPLOYEES
file in which the field NAME contains the value ADKINSON and
processes the selected records. In this example, the processing consists of displaying
certain fields from each record selected.
** Example 'FINDX03': FIND ************************************************************************ DEFINE DATA LOCAL 1 MYVIEW VIEW OF EMPLOYEES 2 NAME 2 FIRST-NAME 2 CITY END-DEFINE * FIND MYVIEW WITH NAME = 'ADKINSON' DISPLAY NAME FIRST-NAME CITY END-FIND END
If the FIND statement contained
a WHERE clause in
addition to the WITH
clause, only those records that were selected as a result of the WITH
clause and met the WHERE criteria would be processed.
The following diagram illustrates the flow logic of a database processing loop:
The use of multiple FIND and/or
READ statements creates a
hierarchy of processing loops, as shown in the following example:
** Example 'FINDX04': FIND (two FIND statements nested)
************************************************************************
DEFINE DATA LOCAL
1 PERSONVIEW VIEW OF EMPLOYEES
2 PERSONNEL-ID
2 NAME
1 AUTOVIEW VIEW OF VEHICLES
2 PERSONNEL-ID
2 MAKE
2 MODEL
END-DEFINE
*
EMP. FIND PERSONVIEW WITH NAME = 'ADKINSON'
VEH. FIND AUTOVIEW WITH PERSONNEL-ID = PERSONNEL-ID (EMP.)
DISPLAY NAME MAKE MODEL
END-FIND
END-FIND
END
The above program selects from the EMPLOYEES file all people with the
name ADKINSON. Each record (person) selected is then processed as
follows:
The second FIND statement is executed to select the automobiles from
the VEHICLES file, using as selection criterion the
PERSONNEL-IDs from the records selected from the
EMPLOYEES file with the first FIND statement.
The NAME of each person selected is displayed; this information is
obtained from the EMPLOYEES file. The MAKE and
MODEL of each automobile owned by that person is also displayed;
this information is obtained from the VEHICLES file.
The second FIND statement creates an inner processing loop within the
outer processing loop of the first FIND statement, as shown in the
following diagram.
The diagram illustrates the flow logic of the hierarchy of processing loops in the previous example program:
It is also possible to construct a processing loop hierarchy in which the same file is used at both levels of the hierarchy:
** Example 'FINDX05': FIND (two FIND statements on same file nested)
************************************************************************
DEFINE DATA LOCAL
1 PERSONVIEW VIEW OF EMPLOYEES
2 NAME
2 FIRST-NAME
2 CITY
1 #NAME (A40)
END-DEFINE
*
WRITE TITLE LEFT JUSTIFIED
'PEOPLE IN SAME CITY AS:' #NAME / 'CITY:' CITY SKIP 1
*
FIND PERSONVIEW WITH NAME = 'JONES'
WHERE FIRST-NAME = 'LAUREL'
COMPRESS NAME FIRST-NAME INTO #NAME
/*
FIND PERSONVIEW WITH CITY = CITY
DISPLAY NAME FIRST-NAME CITY
END-FIND
END-FIND
END
The above program first selects all people with name JONES and first name
LAUREL from the EMPLOYEES file. Then all who live in the
same city are selected from the EMPLOYEES file and a list of these people
is created. All field values displayed by the DISPLAY statement are taken
from the second FIND statement.
Output of Program FINDX05:
PEOPLE IN SAME CITY AS: JONES LAUREL
CITY: BALTIMORE
NAME FIRST-NAME CITY
-------------------- -------------------- --------------------
JENSON MARTHA BALTIMORE
LAWLER EDDIE BALTIMORE
FORREST CLARA BALTIMORE
ALEXANDER GIL BALTIMORE
NEEDHAM SUNNY BALTIMORE
ZINN CARLOS BALTIMORE
JONES LAUREL BALTIMORE
See the following example programs:
This section describes how Natural performs database updating operations based on transactions.
The following topics are covered:
Natural performs database updating operations based on transactions, which means that all database update requests are processed in logical transaction units. A logical transaction is the smallest unit of work (as defined by you) which must be performed in its entirety to ensure that the information contained in the database is logically consistent.
A logical transaction may consist of one or more update statements (DELETE, STORE, UPDATE) involving one or more database files. A logical
transaction may also span multiple Natural programs.
A logical transaction begins when a record is put on "hold"; Natural does
this automatically when the record is read for updating, for example, if a FIND loop contains an UPDATE
or DELETE statement.
The end of a logical transaction is determined by an END TRANSACTION statement in the program. This statement
ensures that all updates within the transaction have been successfully applied, and
releases all records that were put on "hold" during the transaction.
DEFINE DATA LOCAL 1 MYVIEW VIEW OF EMPLOYEES 2 NAME END-DEFINE FIND MYVIEW WITH NAME = 'SMITH' DELETE END TRANSACTION END-FIND END
Each record selected would be put on "hold", deleted, and then - when the
END TRANSACTION statement
is executed - released from "hold".
Note:
The Natural profile parameter ETEOP, as set by the Natural administrator,
determines whether or not Natural will generate an END TRANSACTION
statement at the end of each Natural program. Ask your Natural administrator for
details.
The following example program adds new records to the EMPLOYEES file.
** Example 'STOREX01': STORE (Add new records to EMPLOYEES file)
*
** CAUTION: Executing this example will modify the database records!
************************************************************************
DEFINE DATA LOCAL
1 EMPLOYEE-VIEW VIEW OF EMPLOYEES
2 PERSONNEL-ID(A8)
2 NAME (A20)
2 FIRST-NAME (A20)
2 MIDDLE-I (A1)
2 SALARY (P9/2)
2 MAR-STAT (A1)
2 BIRTH (D)
2 CITY (A20)
2 COUNTRY (A3)
*
1 #PERSONNEL-ID (A8)
1 #NAME (A20)
1 #FIRST-NAME (A20)
1 #INITIAL (A1)
1 #MAR-STAT (A1)
1 #SALARY (N9)
1 #BIRTH (A8)
1 #CITY (A20)
1 #COUNTRY (A3)
1 #CONF (A1) INIT <'Y'>
END-DEFINE
*
REPEAT
INPUT 'ENTER A PERSONNEL ID AND NAME (OR ''END'' TO END)' //
'PERSONNEL-ID : ' #PERSONNEL-ID //
'NAME : ' #NAME /
'FIRST-NAME : ' #FIRST-NAME
/*********************************************************************
/* validate entered data
/*********************************************************************
IF #PERSONNEL-ID = 'END' OR #NAME = 'END'
STOP
END-IF
IF #NAME = ' '
REINPUT WITH TEXT 'ENTER A LAST-NAME'
MARK 2 AND SOUND ALARM
END-IF
IF #FIRST-NAME = ' '
REINPUT WITH TEXT 'ENTER A FIRST-NAME'
MARK 3 AND SOUND ALARM
END-IF
/*********************************************************************
/* ensure person is not already on file
/*********************************************************************
FIP2. FIND NUMBER EMPLOYEE-VIEW WITH PERSONNEL-ID = #PERSONNEL-ID
/*
IF *NUMBER (FIP2.) > 0
REINPUT 'PERSON WITH SAME PERSONNEL-ID ALREADY EXISTS'
MARK 1 AND SOUND ALARM
END-IF
/*********************************************************************
/* get further information
/*********************************************************************
INPUT
'ENTER EMPLOYEE DATA' ////
'PERSONNEL-ID :' #PERSONNEL-ID (AD=IO) /
'NAME :' #NAME (AD=IO) /
'FIRST-NAME :' #FIRST-NAME (AD=IO) ///
'INITIAL :' #INITIAL /
'ANNUAL SALARY :' #SALARY /
'MARITAL STATUS :' #MAR-STAT /
'DATE OF BIRTH (YYYYMMDD) :' #BIRTH /
'CITY :' #CITY /
'COUNTRY (3 CHARS) :' #COUNTRY //
'ADD THIS RECORD (Y/N) :' #CONF (AD=M)
/*********************************************************************
/* ENSURE REQUIRED FIELDS CONTAIN VALID DATA
/*********************************************************************
IF #SALARY < 10000
REINPUT TEXT 'ENTER A PROPER ANNUAL SALARY' MARK 2
END-IF
IF NOT (#MAR-STAT = 'S' OR = 'M' OR = 'D' OR = 'W')
REINPUT TEXT 'ENTER VALID MARITAL STATUS S=SINGLE ' -
'M=MARRIED D=DIVORCED W=WIDOWED' MARK 3
END-IF
IF NOT(#BIRTH = MASK(YYYYMMDD) AND #BIRTH = MASK(1582-2699))
REINPUT TEXT 'ENTER CORRECT DATE' MARK 4
END-IF
IF #CITY = ' '
REINPUT TEXT 'ENTER A CITY NAME' MARK 5
END-IF
IF #COUNTRY = ' '
REINPUT TEXT 'ENTER A COUNTRY CODE' MARK 6
END-IF
IF NOT (#CONF = 'N' OR= 'Y')
REINPUT TEXT 'ENTER Y (YES) OR N (NO)' MARK 7
END-IF
IF #CONF = 'N'
ESCAPE TOP
END-IF
/*********************************************************************
/* add the record with STORE
/*********************************************************************
MOVE #PERSONNEL-ID TO EMPLOYEE-VIEW.PERSONNEL-ID
MOVE #NAME TO EMPLOYEE-VIEW.NAME
MOVE #FIRST-NAME TO EMPLOYEE-VIEW.FIRST-NAME
MOVE #INITIAL TO EMPLOYEE-VIEW.MIDDLE-I
MOVE #SALARY TO EMPLOYEE-VIEW.SALARY (1)
MOVE #MAR-STAT TO EMPLOYEE-VIEW.MAR-STAT
MOVE EDITED #BIRTH TO EMPLOYEE-VIEW.BIRTH (EM=YYYYMMDD)
MOVE #CITY TO EMPLOYEE-VIEW.CITY
MOVE #COUNTRY TO EMPLOYEE-VIEW.COUNTRY
/*
STP3. STORE RECORD IN FILE EMPLOYEE-VIEW
/*
/*********************************************************************
/* mark end of logical transaction
/*********************************************************************
END OF TRANSACTION
RESET INITIAL #CONF
END-REPEAT
END
Output of Program STOREX01:
ENTER A PERSONNEL ID AND NAME (OR 'END' TO END) PERSONNEL ID : NAME : FIRST NAME :
If Natural is used with Adabas, any record which is to be updated will be placed in
"hold" status until an END
TRANSACTION or BACKOUT
TRANSACTION statement is issued or the transaction time limit is
exceeded.
When a record is placed in "hold" status for one user, the record is not available for update by another user. Another user who wishes to update the same record will be placed in "wait" status until the record is released from "hold" when the first user ends or backs out his/her transaction.
To prevent users from being placed in wait status, the session parameter WH (Wait for Record in Hold
Status) can be used (see the Parameter Reference).
When you use update logic in a program, you should consider the following:
The maximum time that a record can be in hold status is determined by the Adabas
transaction time limit (Adabas parameter TT). If this time
limit is exceeded, you will receive an error message and all database modifications
done since the last END
TRANSACTION will be made undone.
The number of records on hold and the transaction time limit are affected by the
size of a transaction, that is, by the placement of the END TRANSACTION
statement in the program. Restart facilities should be considered when deciding
where to issue an END TRANSACTION. For example, if a majority of
records being processed are not to be updated, the GET statement is an efficient way of
controlling the "holding" of records. This avoids issuing multiple
END TRANSACTION statements and reduces the number of ISNs on hold.
When you process large files, you should bear in mind that the GET
statement requires an additional Adabas call. An example of a GET
statement is shown below.
The placing of records in "hold" status is also controlled by the
profile parameter RI (Release ISNs), as set by the Natural
administrator.
** Example 'GETX01': GET (put single record in hold with UPDATE stmt)
**
** CAUTION: Executing this example will modify the database records!
***********************************************************************
DEFINE DATA LOCAL
1 EMPLOY-VIEW VIEW OF EMPLOYEES
2 NAME
2 SALARY (1)
END-DEFINE
*
RD. READ EMPLOY-VIEW BY NAME
DISPLAY EMPLOY-VIEW
IF SALARY (1) > 1500000
/*
GE. GET EMPLOY-VIEW *ISN (RD.)
/*
WRITE '=' (50) 'RECORD IN HOLD:' *ISN(RD.)
COMPUTE SALARY (1) = SALARY (1) * 1.15
UPDATE (GE.)
END TRANSACTION
END-IF
END-READ
END
During an active logical transaction, that is, before the END TRANSACTION statement is issued,
you can cancel the transaction by using a BACKOUT TRANSACTION statement. The execution of this
statement removes all updates that have been applied (including all records that have
been added or deleted) and releases all records held by the transaction.
With the END TRANSACTION
statement, you can also store transaction-related information. If processing of the
transaction terminates abnormally, you can read this information with a GET TRANSACTION DATA statement to
ascertain where to resume processing when you restart the transaction.
The following program updates the EMPLOYEES and VEHICLES
files. After a restart operation, the user is informed of the last
EMPLOYEES record successfully processed. The user can resume processing
from that EMPLOYEES record. It would also be possible to set up the restart
transaction message to include the last VEHICLES record successfully
updated before the restart operation.
** Example 'GETTRX01': GET TRANSACTION
*
** CAUTION: Executing this example will modify the database records!
************************************************************************
DEFINE DATA LOCAL
01 PERSON VIEW OF EMPLOYEES
02 PERSONNEL-ID (A8)
02 NAME (A20)
02 FIRST-NAME (A20)
02 MIDDLE-I (A1)
02 CITY (A20)
01 AUTO VIEW OF VEHICLES
02 PERSONNEL-ID (A8)
02 MAKE (A20)
02 MODEL (A20)
*
01 ET-DATA
02 #APPL-ID (A8) INIT <' '>
02 #USER-ID (A8)
02 #PROGRAM (A8)
02 #DATE (A10)
02 #TIME (A8)
02 #PERSONNEL-NUMBER (A8)
END-DEFINE
*
GET TRANSACTION DATA #APPL-ID #USER-ID #PROGRAM
#DATE #TIME #PERSONNEL-NUMBER
*
IF #APPL-ID NOT = 'NORMAL' /* if last execution ended abnormally
AND #APPL-ID NOT = ' '
INPUT (AD=OIL)
// 20T '*** LAST SUCCESSFUL TRANSACTION ***' (I)
/ 20T '***********************************'
/// 25T 'APPLICATION:' #APPL-ID
/ 32T 'USER:' #USER-ID
/ 29T 'PROGRAM:' #PROGRAM
/ 24T 'COMPLETED ON:' #DATE 'AT' #TIME
/ 20T 'PERSONNEL NUMBER:' #PERSONNEL-NUMBER
END-IF
*
REPEAT
/*
INPUT (AD=MIL) // 20T 'ENTER PERSONNEL NUMBER:' #PERSONNEL-NUMBER
/*
IF #PERSONNEL-NUMBER = '99999999'
ESCAPE BOTTOM
END-IF
/*
FIND1. FIND PERSON WITH PERSONNEL-ID = #PERSONNEL-NUMBER
IF NO RECORDS FOUND
REINPUT 'SPECIFIED NUMBER DOES NOT EXIST; ENTER ANOTHER ONE.'
END-NOREC
FIND2. FIND AUTO WITH PERSONNEL-ID = #PERSONNEL-NUMBER
IF NO RECORDS FOUND
WRITE 'PERSON DOES NOT OWN ANY CARS'
ESCAPE BOTTOM
END-NOREC
IF *COUNTER (FIND2.) = 1 /* first pass through the loop
INPUT (AD=M)
/ 20T 'EMPLOYEES/AUTOMOBILE DETAILS' (I)
/ 20T '----------------------------'
/// 20T 'NUMBER:' PERSONNEL-ID (AD=O)
/ 22T 'NAME:' NAME ' ' FIRST-NAME ' ' MIDDLE-I
/ 22T 'CITY:' CITY
/ 22T 'MAKE:' MAKE
/ 21T 'MODEL:' MODEL
UPDATE (FIND1.) /* update the EMPLOYEES file
ELSE /* subsequent passes through the loop
INPUT NO ERASE (AD=M IP=OFF) //////// 28T MAKE / 28T MODEL
END-IF
/*
UPDATE (FIND2.) /* update the VEHICLES file
/*
MOVE *APPLIC-ID TO #APPL-ID
MOVE *INIT-USER TO #USER-ID
MOVE *PROGRAM TO #PROGRAM
MOVE *DAT4E TO #DATE
MOVE *TIME TO #TIME
/*
END TRANSACTION #APPL-ID #USER-ID #PROGRAM
#DATE #TIME #PERSONNEL-NUMBER
/*
END-FIND /* for VEHICLES (FIND2.)
END-FIND /* for EMPLOYEES (FIND1.)
END-REPEAT /* for REPEAT
*
STOP /* Simulate abnormal transaction end
END TRANSACTION 'NORMAL '
END
This section discusses the statements ACCEPT and REJECT
which are used to select records based on user-specified logical criteria.
The following topics are covered:
The statements ACCEPT and
REJECT can be used in
conjunction with the database access statements:
** Example 'ACCEPX01': ACCEPT IF ************************************************************************ DEFINE DATA LOCAL 1 MYVIEW VIEW OF EMPLOYEES 2 NAME 2 JOB-TITLE 2 CURR-CODE (1:1) 2 SALARY (1:1) END-DEFINE * READ (20) MYVIEW BY NAME WHERE CURR-CODE (1) = 'USD' ACCEPT IF SALARY (1) >= 40000 DISPLAY NAME JOB-TITLE SALARY (1) END-READ END
Output of Program ACCEPX01:
Page 1 04-11-11 11:11:11
NAME CURRENT ANNUAL
POSITION SALARY
-------------------- ------------------------- ----------
ADKINSON DBA 46700
ADKINSON MANAGER 47000
ADKINSON MANAGER 47000
AFANASSIEV DBA 42800
ALEXANDER DIRECTOR 48000
ANDERSON MANAGER 50000
ATHERTON ANALYST 43000
ATHERTON MANAGER 40000
The statements ACCEPT and
REJECT allow you to specify
logical conditions in addition to those that were specified in WITH and WHERE clauses of the READ statement.
The logical condition criteria in the IF clause of an ACCEPT / REJECT statement are evaluated
after the record has been selected and read.
Logical condition operators include the following (see Logical Condition Criteria for more detailed information):
EQUAL |
EQ |
:= |
NOT EQUAL TO |
NE |
¬= |
LESS THAN |
LT |
< |
LESS EQUAL |
LE |
<= |
GREATER THAN |
GT |
> |
GREATER EQUAL |
GE |
>= |
Logical condition criteria in ACCEPT / REJECT statements may also be connected with the Boolean
operators AND, OR, and NOT. Moreover, parentheses
may be used to indicate logical grouping; see the following examples.
The following program illustrates the use of the Boolean operator AND in
an ACCEPT statement.
** Example 'ACCEPX02': ACCEPT IF ... AND ...
************************************************************************
DEFINE DATA LOCAL
1 MYVIEW VIEW OF EMPLOYEES
2 NAME
2 JOB-TITLE
2 CURR-CODE (1:1)
2 SALARY (1:1)
END-DEFINE
*
READ (20) MYVIEW BY NAME WHERE CURR-CODE (1) = 'USD'
ACCEPT IF SALARY (1) >= 40000
AND SALARY (1) <= 45000
DISPLAY NAME JOB-TITLE SALARY (1)
END-READ
END
Output of Program ACCEPX02:
Page 1 04-12-14 12:22:01
NAME CURRENT ANNUAL
POSITION SALARY
-------------------- ------------------------- ----------
AFANASSIEV DBA 42800
ATHERTON ANALYST 43000
ATHERTON MANAGER 40000
The following program, which uses the Boolean operator OR in a REJECT statement, produces the same
output as the ACCEPT statement in the example above, as the logical
operators are reversed.
** Example 'ACCEPX03': REJECT IF ... OR ...
************************************************************************
DEFINE DATA LOCAL
1 MYVIEW VIEW OF EMPLOYEES
2 NAME
2 JOB-TITLE
2 CURR-CODE (1:1)
2 SALARY (1:1)
END-DEFINE
*
READ (20) MYVIEW BY NAME WHERE CURR-CODE (1) = 'USD'
REJECT IF SALARY (1) < 40000
OR SALARY (1) > 45000
DISPLAY NAME JOB-TITLE SALARY (1)
END-READ
END
Output of Program ACCEPX03:
Page 1 04-12-14 12:26:27
NAME CURRENT ANNUAL
POSITION SALARY
-------------------- ------------------------- ----------
AFANASSIEV DBA 42800
ATHERTON ANALYST 43000
ATHERTON MANAGER 40000
See the following example programs:
This section discusses the use of the statements AT START OF DATA and
AT END OF DATA.
The following topics are covered:
The AT START OF DATA
statement is used to specify any processing that is to be performed after the first of a
set of records has been read in a database processing loop.
The AT START OF DATA statement must be placed within the processing
loop.
If the AT START OF DATA processing produces any output, this will be
output before the first field value. By default, this output is displayed
left-justified on the page.
The AT END OF DATA statement
is used to specify processing that is to be performed after all records for a database
processing loop have been processed.
The AT END OF DATA statement must be placed within the processing
loop.
If the AT END OF DATA processing produces any output, this will be output
after the last field value. By default, this output is displayed
left-justified on the page.
The following example program illustrates the use of the statements AT START OF
DATA and AT END OF DATA.
The Natural system variable *TIME has been incorporated into the
AT START OF DATA statement to display the time of day.
The Natural system function OLD has been incorporated into the AT END OF
DATA statement to display the name of the last person selected.
** Example 'ATSTAX01': AT START OF DATA
************************************************************************
DEFINE DATA LOCAL
1 MYVIEW VIEW OF EMPLOYEES
2 CITY
2 NAME
2 JOB-TITLE
2 INCOME (1:1)
3 CURR-CODE
3 SALARY
3 BONUS (1:1)
END-DEFINE
*
WRITE TITLE 'XYZ EMPLOYEE ANNUAL SALARY AND BONUS REPORT' /
READ (3) MYVIEW BY CITY STARTING FROM 'E'
DISPLAY GIVE SYSTEM FUNCTIONS
NAME (AL=15) JOB-TITLE (AL=15) INCOME (1)
/*
AT START OF DATA
WRITE 'RUN TIME:' *TIME /
END-START
AT END OF DATA
WRITE / 'LAST PERSON SELECTED:' OLD (NAME) /
END-ENDDATA
END-READ
*
AT END OF PAGE
WRITE / 'AVERAGE SALARY:' AVER (SALARY(1))
END-ENDPAGE
END
The program produces the following output:
XYZ EMPLOYEE ANNUAL SALARY AND BONUS REPORT
NAME CURRENT INCOME
POSITION
CURRENCY ANNUAL BONUS
CODE SALARY
--------------- --------------- -------- ---------- ----------
RUN TIME: 12:43:19.1
DUYVERMAN PROGRAMMER USD 34000 0
PRATT SALES PERSON USD 38000 9000
MARKUSH TRAINEE USD 22000 0
LAST PERSON SELECTED: MARKUSH
AVERAGE SALARY: 31333
See the following example programs:
Natural enables users to access wide-character fields (format W) in an Adabas database.
The following topics are covered:
Adabas wide-character fields (W) are mapped to Natural format U (Unicode).
The length definition for a Natural field of format U corresponds to half the size of
the Adabas field of format W. An Adabas wide-character field of length 200
is, for example, mapped to (U100) in Natural.
Natural receives data from Adabas and sends data to Adabas using UTF-16 as common encoding.
This encoding is specified with the OPRB parameter and sent to Adabas with the open
request. It is used for wide-character fields and applies to the entire Adabas user
session.
Collating descriptors are not supported.
For further information on Adabas and Unicode support refer to the specific Adabas product documentation.