-
8/14/2019 Logical database in SAP.doc
1/3
Logical database in SAPThe LDB is special type of ABAP program
that combines the contents of certain relateddatabase tables and
retrieve some related data and make it available to application
programs.
In other words, a LDB is a method by which ABAP programs read
and process the data.The se !ence in which the data is s!pplied to
the program is determined by a treestr!ct!re.
The LDB usually consists of the following components:
"tr!ct!re "elections Database programs
Logical databases have a tree structure .A logical database can
contain a ma#im!m of $%%
tables
"APDBP&P is the name of the database program for the logical
database P&P.
How are logical database used
'.Logical databases when generating an ABAP program
The selection screen generated contains the selections (")L)*T+
PTI &" A&DPA-A )T)-"/ of both the logical database and
the
program.
The only database+specific selections displayed on the selection
screen are those needed by the program for data retrieval
p!rposes
0. Logical databases at r!n+time of an ABAP program
At r!n+time, the system processes the events in the program and
in the logical databasein the following order
Before displaying the selection screen, certain initiali1ations
(e.g. calc!lating defa!ltval!es s!ch as key date, etc./ are
performed for the selection screen by the logical
database and the program.The selection screen is displayed and
the !ser enters data in the inp!t fields.
The logical database and the program check that the inp!t is
correct and complete , b!talso that the !ser has the appropriate
a!thori1ations. If an error occ!rs, some fields aremade ready for
inp!t again, so that the !ser can make the
necessarycorrection(s/.
-
8/14/2019 Logical database in SAP.doc
2/3
In the event "TA-T+ 2+")L)*TI &, the ABAP program performs
any preliminarywork (for e#, importing files/.
The logical database reads the selected data and the program
processes it within the 3)Tevents according to the se !ence
specified by the str!ct!re.
In the event )&D+ 2+")L)*TI &, the ABAP program performs
any concl!dingoperations (for e#ample, calc!lating totals,
e#porting files/.
$ . Designing the selection screensThe standard selection screen
of a logical database has a standard layo!t where")L)*T+ PTI &"
and PA-A )T)-" appear in the sequence they are declared, eachon a
new line. The system a!tomatically generates s!ch a screen for each
program thatdoes not have its own selection screen entered in the
attrib!tes.4o! can define yo!r own selection screens for any
logical database . If the attrib!tes of a
program incl!de the n!mber of its own selection screen, the
system !ses this screen as a
model when generating. Any program+specific selections appear
after the databaseselections. The flow logic for s!ch screens is
also generated a!tomatically and thereforecannot be modified. 4o!
cannot delete database selections
Functions of LDB:
Data retrie al :
The personnel data of each employee is loaded into the main
memory where itcan be accessed for processing.
Screening :
)mployees can be selected according to the organi1ational
criteria entered on theselection screen.
).g56o!rly wage earners in a partic!lar personnel s!b area.
There are two types of screening..Person selection and data
selection period.
Person selection defines those employees for whom a report is to
be r!n.
).g.. onthly wage earners in a specific personnel s!b+area.
).g..Personnel n!mber range ).g..2eat!res of
org.Assignment5)mployees who assigned to certain cost center.
).g..)mployee stat!s..Active or inactive.
The data selection period delimits the time period for which
data is eval!ated. 7hen yo! enter the data selection period,the
provide loop retrieves the infotyperecords whose validity period
overlaps with at least one day of this period.
-
8/14/2019 Logical database in SAP.doc
3/3
Authori!ation chec":
This ens!res that the person starting the eval!ation Is
a!thori1ed to access thereport data.
Lagical Data bases in H# ABAP:
P&P P&P*) PAP P*6
