topic Re: why u use logical databases in Application Development and Automation Discussions

why u use logical databases

Former Member — Fri, 29 Jun 2007 10:10:06 GMT

how u used logical database?how is data transferrd to program?corresponding statement in LDB?

Re: why u use logical databases

seshatalpasai_madala — Fri, 29 Jun 2007 10:12:50 GMT

Hi,

Logical databases are programs that does useful tasks like data fetch, Authorization check on behalf of thep program to which you attach them.

Some of the Tasks of LDB's.

Reading the same data for several programs.

The individual programs do not then need to know the exact structure of the relevant database tables (and especially not their foreign key relationships). Instead, they can rely on the logical database to read the database entries in the right order during the GET event.

Defining the same user interface for several programs.

Logical databases have a built-in selection screen. Therefore, all of the programs that use the logical database have the same user interface.

Central authorization checks

Authorization checks for central and sensitive data can be programmed centrally in the database to prevent them from being bypassed by simple application programs.

Improving Performance

If you want to improve response times, logical databases permit you to take a number of measures to achieve this (for example, using joins instead of nested SELECT statements). These become immediately effective in all of the application programs concerned and save you from having to modify their source code.

The data fetch happend with the PUT_XXXX subrotuines in the Logical database programs.

Example:

----

DATABASE PROGRAM OF THE LOGICAL DATABASE TEST_LDB

----

PROGRAM sapdbtest_ldb DEFINING DATABASE test_ldb.

TABLES: lfa1,

lfb1,

lfc1,

bkpf.

----

Initialize selection screen (process before PBO)

----

FORM init.

....

ENDFORM. "INIT

----

PBO of selection screen (always before selection
screen

----

FORM pbo.

....

ENDFORM. "PBO

----

PAI of selection screen (process always after ENTER)

----

FORM pai USING fname mark.

CASE fname.

WHEN 'SLIFNR'.

....

WHEN 'SBUKRS'.

....

WHEN 'SGJAHR'.

....

WHEN 'SBELNR'.

....

ENDCASE.

ENDFORM. "PAI

----

Call event GET LFA1

----

FORM put_lfa1.

SELECT * FROM lfa1

WHERE lifnr IN slifnr.

PUT lfa1.

ENDSELECT.

ENDFORM. "PUT_LFA1

----

Call event GET LFB1

----

FORM put_lfb1.

SELECT * FROM lfb1

WHERE lifnr = lfa1-lifnr

AND bukrs IN sbulrs.

PUT lfb1.

ENDSELECT.

ENDFORM. "PUT_LFB1

----

Call event GET LFC1

----

FORM put_lfc1.

SELECT * FROM lfc1

WHERE lifnr = lfa1-lifnr

AND bukrs = lfb1-bukrs

AND gjahr IN sgjahr.

PUT lfc1.

ENDSELECT.

ENDFORM. "PUT_LFC1

----

Call event GET BKPF

----

FORM put_bkpf.

SELECT * FROM bkpf

WHERE bukrs = lfb1-bukrs

AND belnr IN sbelnr

AND gjahr IN sgjahr.

PUT bkpf.

ENDSELECT.

ENDFORM. "PUT_BKPF

Regards,

Sesh

Re: why u use logical databases

Former Member — Fri, 29 Jun 2007 10:16:49 GMT

A logical database is a special ABAP/4 program which combines the contents of certain database tables. You can link a logical database to an ABAP/4 report program as an attribute. The logical database then supplies the report program with a set of hierarchically structured table lines which can be taken from different database tables.

LDB offers an easy-to-use selection screens. You can modify the pre-generated selection screen to your needs. It offers check functions to check whether user input is complete, correct, and plausible. It offers reasonable data selections. It contains central authorization checks for data base accesses. Enhancements such as improved performance immediately apply to all report programs that use the logical database.

Less coding s required to retrieve data compared to normal internel tables.

Tables used LDB are in hierarchial structure.

Mainly we used LDBs in HR Abap Programming.

Where all tables are highly inter related so LDBs can optimize the performance there.

Check this Document. All abt LDB's

https://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/com.sap.km.cm.highlightedcontent?documenturi=%2flibrary%2fabap%2fabap-code-samples%2fldb+browser.doc

GO THROUGH LINKS -

http://www.sap-basis-abap.com/saptab.htm

http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9bfa35c111d1829f0000e829fbfe/content.htm

http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/frameset.htm

http://help.sap.com/saphelp_nw04/helpdata/en/c6/8a15381b80436ce10000009b38f8cf/frameset.htm

/people/srivijaya.gutala/blog/2007/03/05/why-not-logical-databases

www.sapbrain.com/FAQs/TECHNICAL/SAP_ABAP_Logical_Database_FAQ.html

www.sap-img.com/abap/abap-interview-question.htm

www.sap-img.com/abap/quick-note-on-design-of-secondary-database-indexes-and-logical-databases.htm

http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/content.htm

http://help.sap.com/saphelp_nw2004s/helpdata/en/9f/db9bb935c111d1829f0000e829fbfe/content.htm

Gothru the blog which provides info on LDB's:

/people/srivijaya.gutala/blog/2007/03/05/why-not-logical-databases

Reward points for useful Answers

Regards

Anji

Re: why u use logical databases

Former Member — Fri, 29 Jun 2007 10:37:17 GMT

Hiiiiiii

Logical Databases

Logical databases are special ABAP programs that retrieve data and make it available to application programs. The most common use of logical databases is still to read data from database tables by linking them to executable ABAP programs.

However, from Release 4.5A, it has also been possible to call logical databases using the function module LDB_PROCESS. This allows you to call several logical databases from any ABAP program, nested in any way. It is also possible to call a logical database more than once in a program, if it has been programmed to allow this. This is particularly useful for programs with type 1.

Logical databases contain Open SQL statements that read data from the database. You do not therefore need to use SQL in your own programs. The logical database reads the program, stores them in the program if necessary, and then passes them line by line to the application program or the function module LDB_PROCESS using an interface work area.

Logical Databases - Views of Data

A logical database provides a particular view of database tables in the R/3 System. It is always worth using logical databases if the structure of the data that you want to read corresponds to a view available through a logical database.

The data structure in a logical database is hierarchical. Many tables in the R/3 System are linked to each other using foreign key relationships. Some of these dependencies form tree-like hierarchical structures. Logical databases read data from database tables that are part of these structures.

The diagram illustrates how the R/3 System might represent the structure of a company. A logical database can read the lines of these tables one after the other into an executable program in a sequence which is normally defined by the hierarchical structure. The term logical database is sometimes used to mean not only the program itself, but also the data that it can procure.

Hope this will help you.

Regards,

Mandeep.