SAP NetWeaver AS ABAP Release 740, ©Copyright 2014 SAP AG. All rights reserved.
ABAP Keyword Documentation →
ABAP − Reference →
Obsolete Language Elements →
Obsolete Processing of External Data →
Logical Databases (Obsolete) →
Logical Databases - Components →
Logical Databases - Database Program
The database program of a logical database ldb has the name SAPDBldb. It is used as a container for
subroutines called by the
ABAP runtime environment when a logical database is processing. The order of the calls and how they
combine with events in executable programs or the function module LDB_PROCESS is determined by the structure of the logical database.
A logical database program usually contains the following subroutines.
-
Called once before processing in the logical database, to prepare the database for any multiple calls
by the function module LDB_PROCESS. If a logical database needs to be called more than once consecutively,
the subroutine must exist and its input/output parameter subrc must be set
to zero. If the parameter subrc is not set to zero, the function module LDB_PROCESS raises the non-class-based exception LDB_NOT_REENTRANT.
-
Called once before the selections are edited.
-
Called each time the selection screen is displayed, which means only when associated with executable programs and not in calls of the function module LDB_PROCESS.
-
Called each time a user action is performed on the selection screen, which means only when associated
with executable programs and not in calls of the function module LDB_PROCESS. At the same time, the interface parameters fname and mark are passed to the subroutine.
- fname contains the name of a selection criterion or parameter on the selection screen.
- mark describes the selection mad by the user. If mark
contains a blank, this indicates that the user entered a simple single value or interval selection.
If mark contains "*", this indicates that the user also made entries on the multiple selection screen.
- ldb_process_check_selections
-
Is called instead of the subroutine pai if the logical database is called
without selection screen processing by the function module LDB_PROCESS. This subroutine can check the
selections passed by the function module. The subroutine is called after the parameters and selection
tables of the selection screen are filled by the interface parameters of LDB_PROCESS. If its input/output
parameter subrc is not set to zero, the function module LDB_PROCESS raises
the exception LDB_SELECTIONS_NOT_ACCEPTED. A message in SYMSG format can
be assigned to the structured input/output parameter msg. This message is then available to the caller of the function module in the system fields sy-msg....
-
Called in an order defined by the structure. This subroutine reads the data of the node node
and uses the statement PUT node to
trigger an appropriate GET event in the ABAP runtime environment. This statement
is the central statement of this subroutine. It can be used only in a subroutine of a logical database
whose structure has the node node and whose name starts with put_node.
The PUT statement branches the program flow in accordance with the structure
of the logical database. The read depth is determine by the
GET statements of the application program or by the interface parameter CALLBACK of the function
module LDB_PROCESS. First, the subroutine put_node is edited for the root node. The statement PUT branches the program flow as follows:
- If the subroutine authority_check_node exists in the database program, the statement PUT branches to this subroutine first.
- The PUT statement then triggers a GET event
in the runtime environment. If a related statement GET
node exists in an associated executable program, the corresponding event block is processed.
If the parameter CALLBACK of the function module LDB_PROCESS is filled accordingly, the associated callback routine is called.
- The PUT statement then branches the program flow as follows:
(a)
To the next existing subroutine of a direct successor node, if a lower node (not necessarily the direct
successor) of the associated subtree in the executable program or function module is requested using GET.
(b) To the subroutine of a node at the same level, if the superordinate node branches to a subroutine
of this type and if a node of this type is requested in the executable program or function module using
GET. Here, the PUT statement starts again with
the first step. Branching does not continue in the subroutine of the lowest node in a subtree requested
using GET. Instead, the current subroutine is resumed. If a subroutine
put_node is executed in full, the program flow returns to the PUT statement from which a branch to put_node was made.
- After returning from a subordinate subroutine put_node, the PUT
statement triggers the event GET node LATE in the runtime environment.
-
Called automatically by the statement PUT node. An authorization check for
the node node in question from the structure of the logical database can be incorporated into this subroutine.
-
Called when a selection is made using the search help, to be edited in the key selected in the search
help. ldb is the name of the logical database. The table entries in the search
help tables can be used to read the required entries from the root node from this subroutine.
PUT can then be used to trigger the processing in the program. The subroutine put_node cannot then be called automatically for the root node.
-
Called before an event whose name is passed in the interface parameter event.
Currently, only the value "START-OF-SELECTION" can be assigned to event to execute a subroutine before this time.
-
Called after an event whose name is passed in the interface parameter event.
Currently, only the value "END-OF-SELECTION" can be assigned to event to execute a subroutine after this time.
- par_val, selcrit_val, selcrit-low_val, selcrit-high_val
-
Called if (on the selection screen) the user calls the value help for the parameter par
or the selection criterion selcrit, which must be one of the selections of the logical database.
- par_hlp, selcrit_hlp, selcrit-low_hlp, selcrit-high_hlp
-
Called if (on the selection screen) the user calls the input help for the parameter par
or the selection criterion selcrit, which must be one of the selections of the logical database.
The following internal table exists implicitly and can be used in the program:
-
DATA: BEGIN OF get_events OCCURS 10,
node(10),
kind,
END OF get_events.
In each row, it contains the name of a node of the logical database in the component node.
The component kind indicates whether the node is requested by the user and how:
- "X": Node is addressed using GET and GET LATE.
- "G": Node is addressed using GET only.
- "L": Node is addressed using GET LATE only.
- "W": Node is not addressed using GET or GET LATE.
A subordinate node, however, is addressed using GET or GET LATE.
- " ": Node is not addressed using GET or GET LATE and no subordinate node is addressed either.
Note
When a selection include is created, Logical Database Builder generates
a template based on the existing structure and the selections defined in the selection include. The generated database program consists of multiple include programs:
- DBldbTOP
Contains the introductory program statement and global declarations.
- DBldbXXX Incorporates the following include programs:
- DBldb001, DBldb002, ...
For the subroutines put_node and authority_check_node.
- DBldbFXXX
Subroutines for processing selection screens (initialization, PBO, PAI, ...).
- DBldbSXXX
Subroutine put_ldb_sp for handling search helps.
- DBldbF001, DBldbF002, ... Self-defined include programs for additional functions.
The predefined NODES or TABLES statements and
the predefined names of the automatically created include programs and subroutines cannot be modified.
It is, however, possible to define further include programs or subroutines and modify the ABAP statements
that read data. Self-defined include programs must use the naming convention DBldbFnnn, otherwise they cannot be transported by the logical database.
Example
LFB1 is a successor of LFA1 in the structure of the logical database. The following selection criteria are defined in the selection include:
-
SELECT-OPTIONS: slifnr FOR lfa1-lifnr,
sbukrs FOR lfb1-bukrs.
One possible section of a database program is therefore:
-
FORM put_lfa1.
SELECT * FROM lfa1
WHERE lifnr IN slifnr.
PUT lfa1.
ENDSELECT.
ENDFORM.
FORM put_lfb1.
SELECT * FROM lfb1
WHERE lifnr = lfa1-lifnr.
AND bukrs IN sbukrs.
PUT lfb1.
ENDSELECT.
ENDFORM.
An executable program associated with the logical database contains the lines:
-
GET lfa1.
WRITE lfa1-lifnr.
GET lfb1.
WRITE lfb1-bukrs.
In this example, the runtime environment calls the routine put_lfa1 after
the event START-OF-SELECTION. The statement PUT lfa1
triggers the event GET lfa1. If the corresponding event block has been processed
in the program, PUT lfa1 branches to the subroutine put_lfb1.
From here, the event GET lfb1 is triggered in the program. If LFB1 is the
last node to be read, the processing of the SELECT loop is then resumed in
put_lfb1. If not, a branch to the subroutine put_node
of the next node is performed. At the end of the SELECT loop of the last
node, the SELECT loop of the next node up is resumed. The programming across
nested SELECT loops makes the process flow easier to understand here. This
should be avoided in real logical databases, however, to reduce the number of database reads. The PUT statements also do not branch to the subroutines for authorization checks in this example.
Example
See also Example of a Database Program.